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Vertically aligned ZnO nanowire arrays in Rose Bengal-based dye-sensitized solar cells
Abstract
We fabricate dye-sensitized solar cells (DSSC) using vertically oriented, high density, and crystalline array of ZnO nanowires, which can be a suitable alternative to titanium dioxide nanoparticle films. The vertical nanowires provide fast routes or channels for electron transport to the substrate electrode. As an alternative to conventional ruthenium complex, we introduce Rose Bengal dye, which acts as a photosensitizer in the dye-sensitized solar cells. The dye energetically matches the ZnO with usual KII2 redox couple for dye-sensitized solar cell applications.
... The morphology of photoanode also influences the performance of DSSCs [145]. Different morphologies of photoanode like nanowire [146] and nanorod [147,148] have been explored for DSSC; they have shown improved electron transport behavior and a long electron lifetime. ...
... The PCE (11.8%) was further enhanced with interfacial modification at a photoanode/electrolyte interface using oleic acid [153]. Pradhan et al reported Rose Bengal dye as an alternative to conventional ruthenium-based dye for ZnO nanowire-based DSSC [146]. The Rose Bengal dye has favorable energy band alignment to the ZnO and KI-I 2 redox couple [146]. ...
... Pradhan et al reported Rose Bengal dye as an alternative to conventional ruthenium-based dye for ZnO nanowire-based DSSC [146]. The Rose Bengal dye has favorable energy band alignment to the ZnO and KI-I 2 redox couple [146]. Srinivas et al synthesized anthracene-based sensitizers and reported their adsorption behavior experimentally and in computational studies [154]. ...
The exponential increase in demand for global energy intake in day-to-day life directs us to look for a green and cost-effective energy generation and storage alternative. India being a fastly developing nation with a vast population, requires the alternative energy resource to meet up the energy deficit in an eco-friendly manner and be self-reliant in energy demands. This review aims to compile and assess developments in energy materials research from Indian prospects. Therefore, this paper discusses India's energy scenario by understanding the fundamental concepts and developments of various solar cell technologies and an overview of energy storage systems (batteries and supercapacitors), accentuating the research progress made so far along with future possibilities. This exploratory study reviews the systematic and sequential advances in all three generations of the solar cell, i.e. Si solar cell, thin-film solar cell, dye-sensitized solar cell, and perovskite solar cells. Herein, the discussion is directed at developing novel materials that are efficient, stable, and economical. Moreover, the current status of the high-performance devices for each technology is reviewed in detail. Finally, the prospects, areas of improvement, and future trends in developing cost-effective and efficient energy materials for solar cells and storage devices are highlighted.
... Alternatively, natural dyes may be used to fabricate the DSSC's, which yields much lower but acceptable efficiency of the fabricated cell. However, the natural dyes have some added advantages like easy availability and low cost [8,9]. Way back in 2006, a power conversion efficiency of 11.18% has been achieved [5] with comparatively low cost natural dyes. ...
... Way back in 2006, a power conversion efficiency of 11.18% has been achieved [5] with comparatively low cost natural dyes. A class of dye called Anthocyanins can easily transfer electron to the conduction band of ZnO [8]. While extracted from various plants, Anthocyanins gives different sensitizing performances [9]. ...
... Bookmark not defined. and widely used as photo sensitizers for preparation of DSSCs [8]. This is one of the best photo sensitizer for ZnO photoanode and is much cheaper than Ru-complex dyes [6]. ...
Due to their high efficiencies, along with lower production costs, many researchers are working on dye-sensitized solar cells (DSSCs) over last few decades as a substitute technology for nonconventional energy. Nanostructured ZnO has got many interesting properties such as wide band gap, large exciton binding energy, good exciton stability, and high breakdown strength, which are applicable as DSSC electrodes. This present work compares the device properties of DSSC fabricated using ZnO nanorods on a ZnO film and ZnO nanopowders. Different types of ZnO photoanode and dye combinations are used to study the stability and photovoltaic properties of the DSSC cell. The photovoltaic properties of the ZnO-based DSSC samples were systematically investigated. The photovoltaic properties of fabricated cell obtained are discussed in the light of band structure and density of states of different types of ZnO nanolayers. The ZnO nanorods fabricated through the sol–gel route have more uniform thickness resulting in enhanced photovoltaic properties of the fabricated device.
... The mixtures were stirred for 3 h and then dried at room temperature to cast a film at later stages [10,11]. Also, the ZnO NPs were synthesized by the standard sol-gel method to use as a plasmonic film in the final device configurations [26][27][28]. ...
... The crystalline nature of prepared ZnO NPs is provided by an X-ray diffraction pattern as shown in Fig. 2. Bragg reflections at 32.2 • , 34.5 • , 37.1 • , and 47.6 • correspond to (100), (002), (101), and (102), respectively, and are indexed, by using JCPDS Card No. 89-7102, as hexagonal wurtzite structure of ZnO NPs. The absence of peak shifting and secondary phases attributes to the good crystalline phase of the ZnO structure [27]. By Debye-Scherrer relation, the average crystallite size of the ZnO NPs is calculated by the (100), (002), (101), and (110) dominant peaks as 70 nm [28]. ...
Hybrid solar cells were fabricated by Camellia sinensis blended polyvinyl alcohol (PVA) as an active medium and using zinc oxide (ZnO) incorporated as light scattering nanoparticles (NPs). The power conversion efficiency of such hybrid solar cells was enhanced. This was due to the broad absorption spectra of PVA upon doping with Camellia sinensis and ZnO NPs employed as an interfacial layer. J-V characterization indicated that hybrid solar cells were more efficient than organic solar cells having no ZnO NPs layer. The maximum power conversion efficiency of 6.7% was obtained for the hybrid solar cell with the configuration of Camellia sinensis doped PVA, ZnO NPs thin film, and silver used as an active layer, light scattering particles, and counter electrode, respectively. Minimum efficiency of 3.1% was found in the case of organic solar cells. This work signifies the use of recyclable green resources for solar energy harvesting purposes.
... 60 It is suggested that one dimensional mesoporous metal oxides (TiO 2 and ZnO) are suitable to overcome carrier transport hurdles. [61][62][63] Comparing OSC BHJ technology, DSSC efficiency and stability progression is poor. Low temperature processed technologies V oc and PCE progression aspect, PHJ normal and inverted PSC technologies, 19,21,35,41,42,47 BHJ OSC, 11,13,26,34,36,43,46 and tandem PSC 53,54 are supposed to be most promising by implementing advanced IEM technologies. ...
... The similar effect is reported on ZnO and TiO 2 scaffold IEMs. 73-92 ZnO low work function or electronegativity as compared with TiO 2 but deep valance level have shown variable conduction impacts 14,36,62,65,[72][73][74]85,[87][88][89][90][91] (see Figure 12). As a single electrode ETL photoconductivity, carrier trapping, and hole blocking prospect of TiO 2 is most impending. ...
Emerging solar cell (ESC) carrier's dynamic transfer difficulties and instability at dissimilar material's interface seems to be potential distress. Electrical permittivity influences on photo carrier dynamics of nonpolarized organic and polarized organic‐inorganic perovskite solar cell. ESC electrical efficiency and stability are consider to be managed broadly by carrier accumulation, extraction, and conduction techniques. Active materials optoelectric interaction and carrier accumulation are petite known. Its energetic dealings with dissimilar interface materials how support to faster carrier extraction and conduction are still in haze. In this drill, focus on active to interface materials key properties are imperative to find a way to promote electrical energy conversion and its steadiness. Selected advanced interface engineering materials (IEMs) architectures, conduction, and multifarious relations to active materials for efficient energy transfer ability and stability are reported precisely by the model. The interface structure consistency supports to systematize energy transfer, otherwise, disorder or energy loss is anticipated. Therefore, active material linkage to IEM photophysical, quantum, and choice of materials technologies are focused comprehensively to explore the pathway of ESC stability and efficiency progression.
... The ease in electron transportation may also be the reason for such good T-100 cell efficiency, even though the open circuit potential (V OC ) value, which is the driving force of electron transportation in the device 77 , is the lowest among investigated cells. At this stage, the fill factor (FF) values, mainly understood as energy loss related to inherent resistance in the photovoltaic device 78,79 , seem worth considering. In this case, the FF values do not vary as much as the other photovoltaic parameters of the presented cells, but still, the result registered for the T_100 cell is one of the best, yielding only the one obtained for the T_160 cell. ...
This investigation introduces an innovative approach to microwave-assisted crystallization of titania nanoparticles, leveraging an in situ process to expedite anatase crystallization during microwave treatment. Notably, this technique enables the attainment of crystalline material at temperatures below 100 °C. The physicochemical properties, including crystallinity, morphology, and textural properties, of the synthesized TiO2 nanomaterials show a clear dependence on the microwave crystallization temperature. The presented microwave crystallization methodology is environmentally sustainable, owing to heightened energy efficiency and remarkably brief processing durations. The synthesized TiO2 nanoparticles exhibit significant effectiveness in removing formic acid, confirming their practical utility. The highest efficiency of formic acid photodegradation was demonstrated by the T_200 material, reaching almost 100% efficiency after 30 min of irradiation. Furthermore, these materials find impactful application in dye-sensitized solar cells, illustrating a secondary avenue for the utilization of the synthesized nanomaterials. Photovoltaic characterization of assembled DSSC devices reveals that the T_100 material, synthesized at a higher temperature, exhibits the highest photoconversion efficiency attributed to its outstanding photocurrent density. This study underscores the critical importance of environmental sustainability in the realm of materials science, highlighting that through judicious management of the synthesis method, it becomes feasible to advance towards the creation of multifunctional materials.
... Recently, ZnO which has a similar band gap (~ 3.3eV) like TiO2, appears to be an alternative semiconductor material for the fabrication of high efficiency DSSCs [9]. Comparing with TiO2, ZnO has much higher electron diffusivity and mobility [10][11] which provides a direct conduction pathway for rapid collection of electrons at the substrate of the photoanode. ...
Conductivity and transport properties of a cost-effective and environment friendly chitosan based solid biopolymer electrolytes which form mechanically robust thick film, have been reported here. A maximum ionic conductivity of ∼ 10 ⁻⁴ S/cm has been achieved by optimizing the concentrations of the salt (LiClO 4 ) and the plasticizer (EC) in the biopolymer electrolyte. Ion transport properties of the biopolymer electrolytes are studied from Raman spectroscopy. A dye-sensitized solar cell (DSSC), with a sandwich structure, is fabricated with chemically synthesized ZnO (∼ 60 nm) as the nanoporous semiconductor material coated with Rose Bengal dye as a photosensitizer, the chitosan biopolymer as electrolyte and platinum as counter electrode. Linear Sweep Voltammetry analysis of the DSSCs illustrates the photovoltaic performance of these cells. Without any external addition of redox couple in the biopolymer electrolytic system, a maximum short-circuit current density of J SC = 0.556 mA/cm ² and open-circuit voltage V oc = 0.605 V with power conversion efficiency 0.051 % is achieved by the DSSC.
... ZnO is a promising II-VI semiconductor oxide having unique properties such as wide optical band gap (3.37 eV), great exciton binding energy (60 meV), rich raw material, non-toxicity, chemical and thermal stability, environmental friendliness, and biocompatibility [1][2][3][4][5][6][7]. Because of the mentioned advantages, ZnO films have been commonly used in several applications such as solar cells, sensors, photocatalysts, dye-sensitized solar cells, and light-emitting diodes and lasers [8][9][10][11][12][13][14][15][16][17][18][19][20]. However, low-cost production of ZnO films is important for technological applications. ...
Pure and doped ZnO films are among the promising materials in technological applications, which is constantly developing and seeking innovations. In this study, the effect of Ir element on the structural, optical, electrical, and surface properties of ZnO films produced by ultrasonic spray pyrolysis at different Ir incorporation rates (4% and 8%) was investigated. XRD patterns show that the 4% Ir-doped ZnO film have the best crystallization level. The thickness and band gap values of pure, 4%, and 8% Ir-doped ZnO films were determined as 269 nm, 278 nm, 267 nm, and 3.20 eV, respectively, by using spectroscopic ellipsometry and optical method. Surface properties were analyzed by field emission scanning electron microscopy, and elemental analyses were performed by energy dispersive X-ray spectroscopy. Electrical resistivity values of ZnO:Ir films calculated by the two-point technique were determined to vary between 8.26 × 100 and 6.29 × 102 Ωcm. Besides, the activation and trap energy values of the films from temperature-dependent resistivity measurements were calculated as 1.358–3.977 meV and 18.019–28.307 meV, respectively. It was concluded from all analyses that Ir element has a strong effect on the structural, surface, and electrical properties of ZnO films and Ir-incorporated ZnO films having suitable structural and surface properties can be used as photocatalysts in photocatalytic applications. Moreover, we suggest that p-type ZnO films can be produced using different Ir incorporation rates.
... After that, the organic dyes and (ruthenium-free complex metals) have been developed by researchers. The organic dyes have indicated the good conversion efficiencies when used as sensitizers in (DSSCs), but the synthesis of these dyes is difficult and time-consuming [3,4]. Likewise, in recent years, the natural dyes as (flavonoid, betacyanin, anthocyanin, chlorophyll, tannin, and carotenes) extracted from flowers, leaves, and fruits have gained increased interest for use as sensitizers for (DSSCs) an alternative to synthesis dyes because their materials are available, cheap, non-toxic, environmentally friendly, and do not require the complex techniques for dye extraction [5,6]. ...
In the present work, dye-sensitized solar cells (DSSCs) were fabricated by using natural dye extracted from eight different flowers namely: [(MN1) Turkish Hibiscus sabdariffa, (MN2) Iraqi Hibiscus sabdariffa, (MN3) Rosehips, (MN4) Lavandula, (MN5) Nerium oleander, (MN6) Red Bougainvillea, (MN7) Pomegranate flower, and (MN8) Pink Bougainvillea] extracts as a photosensitizer. The UV-Vis absorption spectra for all eight samples were recorded at room temperature by using a mixture of 0.1 mol.L −1 HCl and ethanol, and also in different solvents. In addition, the effect of the pH value of these dyes on absorbance were investigated. Moreover, the Fourier transform infrared (FT-IR) spectra of all dyes were recorded. The lamp power used to evaluate the DSSCs performance is 1000 W/m 2. The power conversion efficiency (η) of extracted dyes was reached as follows: (MN1) =1.589 %, (MN2) =1.229 %, (MN3) =0.602 %, (MN4) = 0.927 %, (MN5) =0.684 %, (MN6) =1.317 %, (MN7) =1.059 %, and (MN8) =1.149 %.
... It is a xanthenes class photosensitizer having high absorbtion coefficient and absorbs a wide spectrum of solar radiation. It energetically matches the conduction band edge of ZnO and iodine/iodide redox couple for DSSC application (Pradhan et al. 2007, Duffy et al. 2000. Accordingly, ZnO based DSSC performes specifically well when sensitized with Rose Bengal. ...
Effective suppression of dye aggregation on the photoanode surface of dye sensitized solar cells plays a key role in improving solar cell efficiency. Chenodeoxycholic acid (CDCA) is a very popular anti dye aggregation material used in dye sensitized solar cells (DSSC). However, the selection of an improper concentration of CDCA may lead to decreased solar cell efficiency by lowering the open circuit voltage and short circuit current as a consequence of reduced dye loading. The influence of CDCA as a dye co-adsorbent on the performance of DSSCs fabricated using Rose Bengal dye was studied in this paper. The concentration of the CDCA solution was varied to identify the optimum value for the best device performance. Aside from this, the effect of a very thin and compact ZnO blocking layer was also investigated to reduce the charge recombination. With photovoltaic parameters such as short circuit current density (Jsc) = 1.98 mA/cm2, open circuit voltage (Voc) = 0.58 V, and fill factor (FF) = 0.43, the traditional cell displayed an overall conversion efficiency of 0.49%, while the power conversion efficiency was found to be increased to 1.00% (Jsc = 2.80 mA/cm2, Voc = 0.64, FF = 0.58) when CDCA was added at optimised concentration of 8 mM. Reduced dye aggregation and increased electron injection in the presence of CDCA may be accounted for the DSSC's remarkable improvement in the efficiency. Moreover, the combined effect of 8 mM CDCA and the compact ZnO blocking layer dramatically enhanced the efficiency further to 1.22% (Jsc = 3.09 mA/cm2, Voc = 0.66, FF = 60). Electrochemical impedance spectroscopic (EIS) analysis revealed that the addition of CDCA as a co-adsorbent in the dye solution and addition of ZnO blocking layer resulted in significantly improved electron lifetime and reduced electron recombination yielding improved Jsc, Voc and η.
... By analysing the registered I-V curves and the photovoltaic parameters obtained, it may be observed that the photovoltaic conversion efficiencies (η) of TiCl4 modified cells have been spectacularly increased when compared to "as prepared" ones (see Fig. S5). The highest η value was demonstrated by the cell utilizing (9)TiO2-(1)ZnO+TiCl4 material, and it has been about a forty-fold increase when compared with "as prepared" (9) value; still high FF values suggest that recombination effects in these two materials are not related to decreasing in the ability for electron transport across the semiconductor material [95,96]. JSC value usually strongly depends on the amount of adsorbed dye [11], but this is not the case of cells presented in this paper, where the estimated amounts of adsorbed dye (see Ndye value in Table 8 [82,83]. ...
TiO2-ZnO heterostructures with multifunctional photoactive properties were prepared using the two-stage microwave method. The presence of a binary crystalline system (anatase – wurtzite) was confirmed by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM). The multifunctional character of the obtained photoactive materials was evaluated in two different processes – photocatalysis and photovoltaics. Photo-oxidation tests proved that the TiO2-ZnO heterostructures demonstrate high photocatalytic activity in phenol degradation. Furthermore, the prepared titania-based heterojunction systems were employed as precursors of the semiconducting layers in the DSSCs working electrodes. The photovoltaic parameters of the cells, assembled with electrodes post-treated with TiCl4 solution, have been tremendously improved by as much as forty-fold. Additionally, the scientific novelty of the work should be emphasized, resulting from the utilization of microwave-assisted synthetic strategy for the first time to prepare highly efficient photoactive materials with significant application potential in both photocatalysis and photovoltaics (DSSC cells).
... It has peculiar photophysical and photochemical properties, such as: high absorption in all solvents in which it is soluble, high intersystem crossing yield and it shows some fluorescence, it is a photodynamic sensitizer, it bleaches slowly in protic, polar solvents and its spectrum is most diagnostic of its immediate environment. Due to the richness in its properties, it has assumed a peculiar role in different fields of disciplines such as applications in bulk heterojunction solar cells ) and dye-sensitized solar cells (Pradhan et al., 2007;.It is used as a photo sensitizer for the enhancement of conversion efficiency and storage capacity of photo galvanic cells (Gangotri and Bhimwal, 2010), It sensitized TiO 2 film electrode (Zhao et al., 1997). Rose Bengal water solutions quenched by potassium iodide can be used to measure instrument response functions of single photon detectors in the orange-red wavelength region (Szabeiski et al., 2009). ...
... It should be noted that the fill factor (FF) values registered for all devices are very high (>70%), which indicates that the semiconductor manufacturing process developed by our research group ensures high-quality cells. Fill factor is a crucial DSSC parameter and represents, among others, the energy loss caused by series resistance, electrolyte thickness (spacer influence), and counter electrode production quality (Pt layer) [88][89][90]. It may be observed that indeed the TCO resistance (R 1 ) correlates with FF since the highest FF value was observed for DSSC with the lowest R 1 values (see Table 7). ...
A series of pure and doped TiO2 nanomaterials with different Zr4+ ions content have been synthesized by the simple sol-gel method. Both types of materials (nanopowders and nanofilms scratched off of the working electrode’s surface) have been characterized in detail by XRD, TEM, and Raman techniques. Inserting dopant ions into the TiO2 structure has resulted in inhibition of crystal growth and prevention of phase transformation. The role of Zr4+ ions in this process was explained by performing computer simulations. The three structures such as pure anatase, Zr-doped TiO2, and tetragonal ZrO2 have been investigated using density functional theory extended by Hubbard correction. The computational calculations correlate well with experimental results. Formation of defects and broadening of energy bandgap in defected Zr-doped materials have been confirmed. It turned out that the oxygen vacancies with substituting Zr4+ ions in TiO2 structure have a positive influence on the performance of dye-sensitized solar cells. The overall photoconversion efficiency enhancement up to 8.63% by introducing 3.7% Zr4+ ions into the TiO2 has been confirmed by I-V curves, EIS, and IPCE measurements. Such efficiency of DSSC utilizing the working electrode made by Zr4+ ions substituted into TiO2 material lattice has been for the first time reported.
... Both and linearly increased in order: → → ∶ = 1 ∶ 3 → ∶ = 1 ∶ 1 → ∶ → 3 ∶ 1 as shown in Table 3 . The linear increase in was attributed to higher photogenerated excitons [60] . Leaves of Tectona grandis, Tamarindus indica, Eucalyptus globules and flower of Callistemon citrinus were used as photo-absorber in DSSCs-based TiO 2 . ...
Natural dye sensitizers are attractive as an alternative to expensive and rare organic sensitizers in dye-sensitized solar cells. The partial absorption of solar spectrum by solar cell-based natural dye negates its usefulness as the power conversion efficiency (PCE) is poor. Co-sensitization of two or more natural dyes with variant absorption spectra could be a feasible solution. Herein, Carica papaya leaf (P) and black cherry (B) fruit dye extracts were prepared and used as co-sensitizers at different volume concentration ratios (B:P=1:3, B:P=1:1 and B:P=3:1). The optical performance analysis shows that the light-harvesting ability of the device optimized after the co-sensitization at B:P=3:1 significantly improved. The DSSCs-based B and P show PCEs of 0.25% and 0.29%, respectively. The DSSC-based B:P=3:1 shows the highest PCE of 0.56%. Further investigation using cyclic voltammetry (CV) shows that DSSC-based B:P=3:1 has the smallest electron-injection barrier (ΔEe) among all the fabricated DSSCs while DSSC-based B has the highest ΔEe. Also, electrochemical impedance spectroscopy (EIS) reveals that the DSSC-based B:P=3:1 has the least charge flow resistance, thereby reducing charge recombination in the device. Meanwhile, the radius of the DSSCs-based B arc is the largest depicting presence of high charge flow resistance thereby increasing charge recombination in the device. The co-sensitizer, (B:P=3:1), compensates for absorption defects of single dye ((B or P) and improves the photo-response current. Also, it suppresses the charge recombination in the device and improves the PCE of the device.
... the TiO 2 blocking layer results in improved cell performance. The increased number of efficiently transferred photo generated electrons to the TiO 2 electrode results in an improvement in short-circuit current [67]. By suppressing the recombination of electrons injected from excited photosensitizers in the TiO 2 and electrolyte interface, a higher value of open-circuit voltage was obtained [57]. ...
Over the years, researchers have been working on replacing sensitized dye for dye sensitized solar cells (DSSC), because of its low production cost, biodegradability, and non-toxicity. However, the overall performance of natural dye-based DSSCs is low compared to the DSSCs sensitized with Ruthenium based dyes. The combination of natural dyes with an optimized choice of the extracting solvents and the proper volume ratio of mixture of the dyes, enhances inherent properties, such as absorption and adsorption of the dyes. It also allows the device to utilize photon energy more efficiently over the entire visible wavelength. As a result, DSSC sensitized with the dye mixture shows higher absorbance, and cumulative absorption properties over the whole visible region than the DSSC fabricated with individual dyes and showed higher photocurrent. Another effective way to improve cell efficiency is by using a blocking layer. The blocking layer increases the photocurrent, is mainly due to the improvement of the electron recombination at the transparent conducting oxide/electrolyte interfaces. Also, the blocking layer’s compact structure creates an effective pathway for electron transportation; thus, the device’s photocurrent increases. Additionally, a slight improvement in the open-circuit voltage and fill factor was observed, thus cell efficiency enhances significantly. By both the proper ratio of dye mixture and the blocking layer improves cell performance of DSSC and opens a new pathway for future studies.
... This situation can be attributed to the effects associated with an increase in the tendency to recombination of excited electrons, along with an increase in the ZnO content in the system, which favours a decrease in the JSC value. However, the still high FF values suggest that the recombination effects in these two materials are not related to the decrease in the ability for the electron transport across the semiconductor material [38,39]. The slight, but evident, increase in the VOC value observed with the increase in ZnO content in the tested materials (except for the systems with the lowest content of TiO2 and the reference ZnO) could be a consequence of the differences in the position of the ZnO and TiO2 conduction band [40,41]. ...
... Based on our previous studies [15], Rose Bengal dye was identified for further investigation. The Rose Bengal dye absorbs a larger fraction of the solar spectrum in the visible region For measurement of Photovoltaic Properties, I-V characteristics of DSSCs based on nanoporous ZnO fabricated from Nano Powders and ZnO nanorods fabricated through Sol-gel technique, using Rose Bengal dye was recorded [16]. Figure 3(b) shows the photocurrent resistance characteristics for ZnO-nanorod DSSC. ...
Dye sensitized Solar cell (DSSC) is a photo-electrochemical system which converts solar energy into electrical energy. In the present era DSSCs takes so much attention because of their considerably high efficiencies at a comparably low production cost. The nanostructured electrode plays a vital role in device properties. Originally, the nanostructured TiO2 were widely used as DSSC electrodes. Further, nanostructured ZnO has shown a great deal of research interest as the electrode material in DSSCs due to some of its fascinating properties. Compared to other semiconductors, it has unique properties such as large exciton binding energy, wide band gap, high breakdown strength, cohesion and exciton stability. In this paper, the construction and electron transport mechanism of DSSCs devices are described and a comparison of performances of DSSCs fabricated with ZnO or TiO2 photo electrodes was made in terms of its device parameters. This is further correlated with the band structure & density of states (DOS) of ZnO and TiO2 using Density functional theory (DFT) and finally the photovoltaic performance of ZnO and TiO2 based DSSCs was discussed to elucidate the differences.
... As the light intensity increased, the short circuit current value linearly increased to the values close to saturation. The linear increase in (J sc ) was attributed to higher photogenerated excitons [40]. Therefore, more electron densities were transferred to ZnO at higher light intensities. ...
In the present study, we report on the synthesis of ZnO nanoparticles using Tilia Tomentosa (Ihlamur) leaves extract followed by calcination at 400 C for 15 min. The prepared ZnO nanoparticles were characterized by XRD and SEM to study the phase and microstructure, respectively. The XRD analysis showed the absence of impurity peaks and the SEM image confirmed the spherical nature of the prepared ZnO nanoparticles with an average particle size of 80 nm. UV-Visible spectroscopy was used to study the optical properties, and the bandgap was calculated to be 3.55 eV. This large bandgap is attributed to the property of the semiconductor, which can be explored for solar cell applications. Therefore, we used green synthesized ZnO nanoparticles to fabricate dye-sensitized solar cells (DSSC). From the J-V curves, we calculated the DSSC parameters such as open-circuit voltage (V oc), short circuit current density (J sc), fill factor (FF) and efficiency (h), and their values were 0.65 V, 6.26 mA, 48.5%, and 1.97%, respectively, at 100 mW/cm 2 .
... This observation can be explained with the higher efficiency of the excited electron recombination process in the former four cells when compared to two latter. J SC values should be considered in pair with the FF values, to support the above interpretation, as it is well known that FF is the indication of the energy loss (e.g., via recombination) related to inherent resistance in the DSSC device [23,24]. The FF values of investigated cells strongly depend on the concentration of Pt precursor used for CE preparation, and they increase with the concentration increase up to 90 mM. ...
The new, fast, and simple preparation method of counter electrodes for dye-sensitized solar cells has been presented and the optimization of the Pt precursor solution concentration has been described. The counter electrodes prepared with the use of the Pt precursor solutions in six different concentrations have been applied for the solar cells assembly and the parameters of the devices have been well characterized with photocurrent-photovoltage measurements and electrochemical impedance spectroscopy experiments. 90 mM has been found as an optimal concentration of Pt precursor solution.
... It has higher electron mobility than TiO2 and lower recombination probability [Kanmani et al., 2012;Plank et al., 2009]. ZnO based solar cells can be fabricated at low cost using environmentally friendly materials: zinc oxide and natural dye extraction from locally available fruits and flowers [Pradhan et al., 2007]. One of the hindrances so far of ZnO based DSSCs with natural dyes is low efficiency. ...
We have grown Zinc Oxide (ZnO) nanosheet layers on bare glass and conducting Fluorine doped tin oxide (FTO) glass substrates by hydrothermal route. Aluminum doped ZnO (AZO) layer was deposited using a spin coating method prior to growth of ZnO nanostructures which is then used as a seed layer in hydrothermal growth. As-grown zinc oxide films' structure, surface morphology and optical properties were studied by using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Ultraviolet Visible (UV-Vis) Spectrophotometer, respectively. XRD study confirmed hexagonal wurtzite structure of ZnO orienting along (002) planes. Scanning Electron Microscope image clearly shows the growth of nanosheet like structures of ZnO. The optical band gap of ZnO film deposited on glass substrate was found to be 3.25eV. We have also studied the influence of growth time on band gap of as grown ZnO film grown on FTO coated substrates. Out results showed that the band gap energy was decreased from 3.21eV to 3.16eV for the increase of growth time fr om 2 hours to 4 hours. We have used Vitis vinifera dye extraction as the natural dye sensitizer in the fabrication of dye-sensitized solar cell (DSSC). Our experimental results on I-V measurement of assembled DSSC showed maximum short circuit current and o pen circuit voltage of about 30 microampers and 600 millivolts, respectively.
... ZnO nanorods were grown on the ITO coated glass substrate by following a simple two-step Sol-Gel spin coating protocol followed by hydrothermal growth. 30 In the first step, a thin ZnO seed layer was formed on the ITO glass substrates using 5 mM Zinc acetate dehydrate CH 3 COO) 2 Zn, 2H 2 O, (98% Merck) in acetone as precursor solution. The solution was well mixed using an ultrasonic bath for 2 hours at room temperature and then spun onto cleaned and masked ITO coated glass substrates using a programmable spin coater (Apex Technologies, Model SCU-2008C) at 1000 rpm for 30 seconds. ...
The present work reports comparative assessment of optical and electrical properties of DSSCs fabricated using vertically aligned ZnO nanorods synthesized using low cost Sol-Gel spin coating technique on ITO coated glass substrate and ZnO nanopowder and their application in the fabrication of natural dye based Dye Sensitized Solar Cells. Natural dyes extracted from pomegranate and turmeric are used sensitizers. The surface morphology and crystal structure have been investigated by scanning electron microscopy and X-ray diffraction techniques. Optical absorption properties of the dyes were studied using UV-VIS spectroscopy. Photovoltaic parameters like Open Circuit voltage (VOC), Short Circuit current (ISC), fill factor (FF), Energy Conversion efficiency (η) were calculated to study the performances of the cells. Cell parameters like series resistance (Rs) and shunt resistance (Rsh) were calculated from the I-V curve. Electrochemical impedance spectroscopy (EIS) was employed for detail investigation of the charge carrier recombination properties and the charge transfer mechanism at different interfaces of the DSSC devices. Various cell parameters were determined by fitting the experimental EIS curves with the appropriate equivalent circuit. The electron lifetimes were determined using bode plot of EIS measurement for the ZnO nanorod and ZnO nanoparticle photo electrodes sensitized using curcumin dye from turmeric and anthocyanin dye from pomegranate juice. The ZnO nanorod sensitized with curcumin cell emerged out as the best performing cell among the four cells which can be attributed to the highest electron lifetime, higher recombination resistance resulting in lower charge carrier recombination in the ZnO/Dye/Electrolyte interface. Many researchers have studied sensitizing effect of curcumin dye with different nanostructures of ZnO, but we are the first to study the sensitizing effect of curcumin dye on ZnO nanorod like structure.
... DSSCs present a pronounced challenge to silicon-based semiconductor solar cells in the photovoltaic market because of their superior performance under diffuse light conditions and low illumination levels, independent of incident light angle, and cost-effective means of manufacturing and energy conversion (Figgemeier and Hagfeldt, 2004;Furube et al., 2004;Han et al., 2012;Yang et al., 2011;Robson et al., 2011;Wu et al., 2012) makes DSSCs a favourable alternative to traditional silicon solar cells as a method of converting solar energy to electricity and thus providing an effectively uninterruptible source of energy. This superior performance of DSSCs is because of their independence on the angle of incident light and high sensitivity during low levels of illumination (Pradhan et al., 2007). Dye-sensitized solar cells (DSSCs) were explored by (O'Regan and Grätzel, 1991), which exhibited significant improvements in the total conversion efficiency of DSSCs reaching up to 11.2% for N719, which was performed on a spot cell. ...
Two novel high molar extinction coefficient monosubstituted-bipy Ru (II) complexes, IA-5 and IA-6, based on D-D-π and π-A-π-A ancillary ligands were synthesized with the aid of Knoevenagel reaction, to study the influence of the electron donor and electron acceptor ancillary ligand and number of anchoring group (COOH) on the light harvesting efficiency (LHE), ground and excited state oxidation potentials, incident-photon-to-current conversion efficiency (IPCE), short-circuit photocurrent density (J), and total solar-to-electric conversion efficiency (%η) for DSSCs, and their device performances were studied and showed a maximum of PCE of 7.81% (J SC = 17.61 mA cm −2 , V OC = 0.69 V and FF = 64.05%) for dye IA-6 compared to PCE of 7.74% (J SC = 15.83 mA cm −2 , V OC = 0.74 V and FF = 65.37%) for N719 dye. The photophysical and photoelec-trochemical properties discussed herein addressed the significant impact of the electron donor and electron acceptor ancillary ligand and the number of anchoring groups on J SC and %η in DSSCs. The molecular structures of IA-5 and IA-6 were characterized using UV-Vis, emission spectrophotometry, FT-IR, ESI-MS, and 1 H NMR. To probe the interrelationship between the chemical structure, photophysical and photoelectrochemical properties, molecular modeling studies, implemented in Gaussian, were employed. DFT/TD-DFT calculations were used to calculate the thermodynamics and electronic properties of IA-5 and IA-6 including HOMO and LUMO isosurfaces, lowest singlet-singlet electronic transitions (E 0-0), ground and excited states oxidation potentials , GSOP and ESOP, which were in excellent agreement with the experimental results. Surprisingly, the insertion of the strong electron acceptor benzodithiazole in the ancillary ligand of IA-5 showed that the frontier LUMO shifted by 100% from 2,2′-bipyridyl-4,4′-dicarboxlic acid to the ancillary ligand containing benzo-dithiazole with electron injection accomplished from the anchoring group tethered to benzodithiazole. This new finding of relocating the LUMO from bipy-dicarboxylic acid to the other ancillary ligand would open the door for the molecular engineering of better light harvesting and more efficient Ru (II) complexes for dye-sensitized solar cells.
... Meanwhile, the decrease in R 2 could explain the higher fill factor (FF) values of P25-GD DSSCs. It is well known that the FF values reflect the energy loss related to inherent resistances of the DSSCs, which mainly includes the resistance at TiO 2 /dye interface and that of TiO 2 photoanode [46]. Thus, in our system, higher FF values of cells using P25-GD photoanodes were achieved due to the smaller R 2 and less energy loss of the devices. ...
As a novel two-dimensional material consisting of sp- and sp2-hybridized carbon atoms, graphdiyne (GD) shows great potentials in the field of electric and material science. In particular, the performance is reported to be significantly improved for GD-involved optoelectronic devices due to its excellent electronic properties. Herein, to facilitate the charge transfer process and further improve the photo-to-electricity conversion efficiency (PCE) for dye-sensitized solar cells (DSSCs), for the first time we introduced GD in the TiO2(P25)-based photoanodes of DSSCs, resulting in GD-doped TiO2 photoanodes. It was shown that the overall performance of the GD-doped cell is significantly enhanced due to the higher dye adsorption amount, faster electron transfer and lower recombination, compared to that of the undoped DSSC. Furthermore, the optimum GD doping amount (weight percent, wt%) was determined. Thus, the DSSC involving P25-0.6 wt% GD photoanode achieved the best PCE of 8.03%, which increased by 26.5% comparing with that of pure P25 film-based cell.
... Several simple organic dyes, and especially xanthene dyes (Eosin Y, Rose Bengal, etc.), yield efficiencies comparable to those achieved with ruthenium complexes, especially when used to sensitize ZnO films (Guillén et al., 2008;Plank et al., 2009;Pradhan et al., 2007). Organic dyes such as these are inexpensive (Kroon et al., 2007), can be easily recycled (Lee et al., 2006) and do not rely on the availability of precious metals such as ruthenium. ...
... , after calculating the following parameters open-circuit voltage Voc, short-circuit current density Jsc and fill factor FF.[13] . ...
... , after calculating the following parameters open-circuit voltage Voc, short-circuit current density Jsc and fill factor FF.[13] . ...
It became a great interest Dye-sensitized solar cells (DSSC) as a successful alternative to silicon solar cells in terms of cost and simplicity. These cells rely on a semi-conductive material of electricity TiO2 nanocrystalline which encapsulates glass electrodes from the connected side at a temperature 450°C. In this work, the effect of nanoparticle size shows the size of atoms. The smaller the size of the atoms, the greater the surface area and thus the sufficient absorption of the dye and the stimulation of electrons, where increasing surface area increases efficiency. Then a limited amount was added and at a certain concentration, which led to a reasonable improvement in efficiency. According to this procedure commercially available TiO2 (10 nm,25 nm,33 nm, 50 nm) standard. A TiO2 paste was prepared by mixing commercial TiO2, ethanol, distilled water, F:SnO2 (FTO film thickness 14 μm) conductive glasses. By using Dr. Blade method we got films with appropriate thicknesses, then by using several particle sizes (10 nm, 25 nm, 33 nm, 50 nm),many efficiencies were founded (2.39 %, 2.1 %,1.85 %,1.65%) respectively. Improved solar cell efficiency after addition of several chemical materials and the best that got is Cu (NO3)2. Efficiency became for (10 nm) (2.61 %, 2.34 %,2.1%,1.85%) respectively under 40 mW/cm².
... To investigate the influence of different types of metal oxide semiconductors as blocking layers on the photovoltaic performance of the Zn 2 SnO 4 -based DSSCs, the current density-voltage (J-V) curves of the fabricated DSSCs were measured under AM 1.5 illumination (100 mW/cm 2 ) which are shown in To realize the reason of these improvements, we firstly focus on the main parameters which can affect the value of short-circuit current density. In brief, the value of J SC in DSSCs is a result of light harvesting efficiency (influenced by three factors: surface area, dye loading and scattering effects), charge injection efficiency (which is related to the electron injection from the excited dye molecules to the conduction band of the metal oxide semiconductor) and charge collection efficiency (defined as the number of electrons that effectively reach the FTO electrode) [30][31][32]. The charge collection efficiency is mainly governed by the charge transport and recombination rate [33]. ...
Charge recombination at interfaces is one of the main factors that limit the power conversion efficiency of dye-sensitized solar cells. In this work, to reduce the charge recombination at the transparent conductive oxide/mesoporous Zn2SnO4 interface and then to improve the photovoltaic performance, different types of metal oxide semiconductor thin films (including SnO2, TiO2 and ZnO) are deposited on the FTO substrate by thermal evaporation method. The results reveal that in comparison with SnO2 and ZnO, the TiO2 dense layer acts as the most appropriate blocking layer for suppressing the charge recombination and increasing the short-circuit current density and power conversion efficiency of the fabricated device. Furthermore, because of the formation of energy barrier at the FTO/Zn2SnO4 interface, the charge recombination rate is minimized and the injected electrons from the excited dye molecules into the conduction band of Zn2SnO4 are accumulated in its conduction band which leads to upward shift of the Fermi level and increases open-circuit voltage. The maximum power conversion efficiency of 3.02% with short-circuit current density of 7.36 mA/cm² and open-circuit voltage of 664 mV is obtained for the device comprising TiO2 blocking layer.
... The V OC parameters correspond to the Fermi level of the semiconductor and the Nernst potential of the redox couple and our results confirm that the materials studied have optimal energetic distance between these two physical features. Fill factors (FF), which represent the energy loss related to inherent resistance of photovoltaic device [27,28] are also on a reasonable level, between 48.2 and 60.7 for RM5 and T2 cells, respectively. On the other hand, unfortunately the short-circuit photocurrent densities (J SC ) values are very low, between 0.48 and 1.14 mA × cm −2 for RM5 and T1 cells, respectively. ...
A series of dye-sensitized solar cells have been constructed using titania-rich paper industry waste materials. The cells obtained were able to produce solar electricity, but with relatively poor photon-to-current efficiencies reaching only 0.47% and short circuit photocurrent densities up to 1.14 mA×cm-2, but reasonable fill factors and very good open circuit photovoltage reaching 67% and 719 mV, respectively. The titania-rich waste samples were prepared by removal of water and post-production organic residues and well characterized with XRD, XRF, FT-IR, SEM, TEM, EDS and UV-Vis techniques. This paper presents an alternative solution for green energy production and conversion of pollutants to useful materials.
... Dye sensitized solar cells (DSSCs) have attracted much attention since their discovery by Gratzel and Regan owing to the easy handling and low cost fabrication [1]. A DSSC works by absorbing light and electrochemically producing electrons from the photons [2] and consists of a dye adsorbed on nanocrystalline TiO 2 based photoanode, a counter electrode (CE) and a redox couple [3]. Various studies have been conducted to improve the overall light conversion efficiency of DSSCs to the level of silicon based solar technology. ...
DNA templated gold wires (AuWs) were fabricated on Pt sputtered ITO (Pt/ITO) substrates using ‘scribing’ or ‘writing’ method to be used as a modified counter electrode (CE) in Dye sensitized solar cells. The gold nanoparticles (AuNPs) bind to DNA in aqueous solution due to the polyanionic nature of DNA. When a scribe is made on the dropcasted Au-DNA solution, the diffusion of Au-DNA complex occurs towards the edges of the scribe due to the coffee ring effect. Capillary force induces evaporation of water that also forces the Au-DNA complex to migrate towards the scribed edges. Meanwhile, the AuNPs are reduced on the surface of DNA to form active seed for nucleation and growth of AuWs. DNA molecules act as a scaffold to arrange the nanoparticles into well-connected submicron to nanoscale wires. The cyclic voltammetry measurements showed that AuWs/Pt/ITO CE exhibited better electro-catalytic activity and higher conductivity than conventional Pt/ITO CE due to the synergistic effect of Pt and AuWs network on ITO. The DSSC fabricated using TiO2 photoanode, N719 dye, I3⁻/I⁻ electrolyte and AuWs/Pt/ITO CE showed a 36% increase in efficiency as compared to the cells made under same parameters but using conventional (Pt/ITO) CE.
... The electrons travel to the counter electrode through the external circuit to reduce the iodide ion of the electrolyte. The iodide ions transport the electrons back to the dye [4]. ...
Natural dyes of anthocyanin extract from flame tree flower (Delonix regia) and chlorophyll extract from pawpaw leaf (Carica papaya) were used as sensitizer to fabricate dye sensitized solar cell (DSSC). The photoelectrode were subjected to UV/Vis spectrophotometer to view their absorbability. The photo electrochemical performances of DSSCs obtained from I.V characteristics showed conversion efficiency, (ɳ) of 0.80 % for the dye extracts from flame tree flower (anthocyanine), with open-circuit voltage (VOC) of 0.5249 mV, short-circuit current density (Isc) of 44.6191 mA/m2 and Fill factor (FF) of 0.5837. Chlorophyll dyes extract from pawpaw leaf has VOC, Isc, FF and conversion efficiency, (ɳ) of 0.5249 mV, 16.5283 mA/m2, 0.5585 and 0.27 % respectively. The conversion efficiency for the mixed dyes (anthocyanin and chlorophyll) at ratio 1:2 is 0.23 % with VOC, Isc and FF of 0.5500 mV, 14.2750 mA/m2 and 0.5451 respectively, while the dye mixture at ratio 1:4 achieved VOC of 0.5249 mV, Isc of 18.4941 mA/m2, FF of 0.5206 and conversion efficiency (ɳ) of 0.26 %. Anthocyanine from flame tree flower dye extract had the higher conversion efficiency of 0.8 % which could be better in term of application in dye solar cell.
... That is to be removed, leaving tiny holes in nano layers resulting in better dye absorption and consequently better contact between ZnO materials. In consequence, it optimizes the chances of electrons being excited by the photons and increases the amount of excited electrons entering into the ZnO conduction bands [24]. The coated ZnO and ZnO/TiO2 photoanodes immersed in different dye solutions such as Alizarin, Purpurin, Quinizarin and N3 dye solutions respectively with the appropriate amounts. ...
This article focuses on the importance of Dye Sensitized Solar Cells (DSSCs) which use the combination of ZnO and ZnO/TiO2 based semiconducting materials that capture a large range of photon energies in the solar spectrum. The nanoparticles ZnO/TiO2 were prepared by using simple chemical precipitation method. The materials were characterizations using powder X-ray diffraction (XRD), UV–Vis absorption spectra and Field emission Scanning electron microscope (FE-SEM) with Energy dispersive analysis of X-ray (EDAX). The efficiency of the material was calculated in order to know its suitability for the fabrication of DSSCs. The results confirm that the combination of ZnO with TiO2 nanomaterials show higher conversion efficiency with naturally extracted Anthroquinones dyes. This material combination is a highly promising agent for the enhancement of the conversion efficiency for the fabrication of high efficient, low cost and high stable DSSCs.
... This could be due to their lack of the carboxylic acid groups forming ester bonds with the oxide [10], as they do in the case of N-719. There were works on RB sensitized ZnO nanowires, yielding much lower J SC ~0.1 mA/cm 2 at ¼ of our cell area which could favor this assumption [11]. However, since TiO 2 was shown to work well with the RB dye yielding J SC ~3 mA/cm 2 and η = 2.09% [12] the ester bond hypothesis has to be put away. ...
We show that by subsequent sensitization of nanostructured ZnO photoanodes with N-719 and Rose Bengal dyes an improvement or worsening of the cell efficiency may be obtained, relating to photoanodes sensitized with N-719 dye only ( JSC = 2.97 mA/cm ² , VOC = 0.68 V, η = 0.99%) depending on the order in which the dyes are applied. We observe that for the case when the N-719 dye is followed by Rose Bengal an increase in efficiency, short circuit current and open circuit voltage is observed ( JSC = 3.95 mA/cm ² , VOC = 0.71 V, η = 1.26%), which we relate to the cascade band alignment of the ZnO and the dyes. In the case when Rose Bengal is first on ZnO followed by N-719, a lowering of all parameters is observed ( JSC = 2.86 mA/cm ² , VOC = 0.64 V, η = 0.94%) due to the trap band alignment. Electrochemical impedance spectroscopy measurements and modelling confirmed this theory showing longer electron lifetimes in the photoanode for the cascade band alignment, enhancing electron-hole separation, than for the trap alignment, facilitating electron-hole recombination.
... Zinc oxide (ZnO) nanoparticles have attracted a great deal of attention in recent years due to its intriguing physical properties: wide band gap (∼3.37 eVat ambient temperature (T a )), large excitonic energy (∼60 meV at T a ), size, and thermal stability (Bouzourâa et al. 2016). ZnO nanoparticles have various applications in many fields such as antimicrobial agent (Olson et al. 2006), piezoelectric transducers (Zhou et al. 2008), photovoltaic devices (Law et al. 2005), gas sensors (Shinagawa et al. 2014), biosensors (Pradhan et al. 2007), transistors (Bashir et al. 2009), optoelectronic devices (Djurišić et al. 2010), and photocatalysts (Wahab et al. 2011). However, because of their large surface area and high surface energy, ZnO nanoparticles aggregate easily. ...
Polyacrylonitrile/zinc oxide (PAN/ZnO) composite nanofiber membranes with different ZnO morphologies were fabricated by repeatedly alternating hot–cold immersion and single alternating hot–cold immersion methods. The influence of the PAN/ZnCl2 ratio and different immersion methods on the morphology, microstructure, and properties of the nanofiber membranes was investigated by using field-emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), and ultraviolet–visible (UV–Vis) spectroscopy. A possible mechanism for different morphologies of PAN/ZnO nanofiber membranes with different PAN/ZnCl2 ratio through different immersion processes was presented, and well-dispersed ZnO nanorod clusters with smallest average dimeter of 115 nm and hexagonal wurtzite structure were successfully anchored onto the PAN nanofiber surface for R-7/1 nanofiber membrane. Compared to S-5/1 prepared by single alternating hot–cold immersion method, the PAN/ZnO nanofiber membrane fabricated by repeatedly alternating hot–cold immersion method (especially for R-7/1) showed improved thermal stability and high photocatalytic activity for methylene blue (MB). Compared to S-5/1, decomposition temperature at 5% weight loss (T5%) was increased by 43 °C from 282 to 325 °C for R-7/1; meanwhile, R-7/1 showed higher photocatalytic degradation ratio of approximately 100% (after UV light irradiation for 8 h) than 65% for S-5/1 even after irradiation for 14 h. Moreover, the degradation efficiency of R-7/1 with good reuse stability remained above 94% after 3 cycles.
Graphical abstractA facile route was presented to fabricate uniform zinc oxide nanorod clusters on polyacrylonitrile nanofiber membranes with superior thermal stability and photocatalytic activity for methylene blue (excellent recyclability).
XRD and SEM images of ZnO nanoparticles prepared by the precipitation method allow investigation of their morphology and morphological refinement. No contamination was observed in the XRD spectrum and SEM confirmed that the nanoparticles were wellcoordinated ZnO at 30 nm size. UV-Vis spectroscopy was used to tune the optical properties and they appeared not to be fixed at 3.34 eV. The band gap of semiconductor materials makes them competitive for solar cell applications. The O-rich stoichiometry measured by XPS may be a direct result of zinc deficiency. Therefore, ZnO nanoparticles were prepared to fabricate secretory solar cells (DSSCs). From the perspective of J-V, open circuit voltage (Voc), barrier thickness (Jsc), fill factor (FF) and efficiency (η) were not chosen as much as possible and the quality was calculated as 0.65V, 6.26mA. , 62.2% and 1.96% respectively at 100mW/cm2 .
In this work, we report an energy upconversion system based on triplet-triplet annihilation comprised of rose bengal dye as the sensitizer and a highly fluorescent 9-(triphenyl)ethynyl-10-phenylanthracene (TPE-PAn) as the triplet annihilator. The energy upconversion can be observed with a low-power laser excitation at 532 nm or noncoherent Xe arc lamp excitaion at 540 nm. A delayed fluorescence from (TPE-PAn) at 418 nm was observed with an energy upconversion up to 0.64 eV and quantum yield of 0.8 %. A white-light emission was achieved as a result of combination of delayed fluorescence from TPE-PAn and residual fluorescence from rose bengal dye.
Recent advances in nanomaterials with basic building blocks such as quantum dots, nanoparticles, nanotubes, nanowires, and nanorods are having a great impact on the development of next-generation, highly efficient, and/or low-cost solar cells. Safe and simple solution phase synthesis that yields nonaggregated, monodispersed, passivized semiconductor nanoparticles of high optoelectronic properties have opened a new door to photovoltaic devices currently being explored. Dye-sensitized solar cells (DSSCs) have been an attraction for many researchers and readers as one of the third generation of photovoltaic technologies that have grown rapidly over the past few decades. The first section of this chapter describes with an introduction the scientific history, construction, and working principles of DSSCs. This is complemented by an understanding of each component, the requirements and properties of devices, followed by the fabrication of DSSCs. We have added basic characterization techniques used to study DSSCs, such as current–voltage (I–V) characteristics and incident photon-to-current conversion efficiency measurements. Cost issues and advanced colorful approaches toward enhancements in efficiency are also discussed.
The research paper reports on a systematic study of structural and optical properties of ZnO nano rods for Solar Applications. Zinc acetate dihydrate and ethanol were used as a starting material and solvent respectively. Zinc oxide (ZnO) thin films were deposited on an ordinary glass substrate by dip coating technique. The crystal structure and orientation of the ZnO nano rods were investigated by X-ray diffraction (XRD) patterns. X-ray diffraction patterns indicated that the grain size increased with increasing annealing temperature. The optical absorbance and transmittance measurements were recorded by using a UV visible spectrophotometer. The UV visible is absorption spectra showed that the band edge absorption at the ZnO band edge was strong, and the band gap of the films annealed at 500 o c. An improved hydrothermally grown ZnO Nano rods were prepared and investigated using sol-gel dip coating method for Solar Applications.
The present paper describes the galvanic (electrochemical) synthesis of CdSe thin films on FTO (Fluorine doped tin oxide) coated glass substrates. The phase and surface microstructure of the coatings were characterized using X-Ray Diffraction(XRD), Field Emission Scanning Electron Microscopy(FESEM), Transmission electron microscopy(TEM). Elemental state composition of annealed CdSe films containing Pd was analysed using X-ray photoelectron spectroscopy(XPS). Spectroscopic analyses were carried out with UV-Vis spectroscopy. Photocatalytic degradation study of toxic dyes and photoreduction of metal ions in solution were carried out with these films to ascertain their utility as an efficient material for wastewater treatment. Electrocatalytic behaviour was established by carrying out Oxygen Evolution Reaction (OER) with these CdSe films as electrodes. Thermoelectric power (S) and thermal conductivity (Ƙ) measurements were performed to identify their potential as thermoelectric material.
Composite layered structure of TiO2 nanoparticles (TiNPs) and TiO2 nanotubes (TiNTs) was prepared by two-step anodizing of titanium at 50 V to form well-aligned TiNTs with uniform diameter, followed by spin coating the TiNPs of 10–30 nm prepared by hydrothermal synthesis. For smaller number of cycles, the spin coated nanoparticles were observed to penetrate into the nanotubular structure up to some extent. Morphology of the samples was studied by scanning electron microscopy (SEM). X-ray diffraction and Raman spectroscopy showed that TiNPs were composed of a mixture of brookite, anatase and rutile phases. Diffuse reflectance spectroscopy (DRS) was performed to assess the light scattering properties and measuring band gap. Photoluminescence spectroscopy was performed to assess the presence of defect. The DSSC made by five times spin coated photoanode shows percentage increase in efficiency of about 55% under back side xenon lamp irradiation. The good light scattering ability of the mixed layer formed by the penetration of nanoparticles without deteriorating the electron transport properties of the high aspect ratio nanotubes offered synergistic effects on the performance of DSSC in backside illumination mode.
A series of sensing hybrid-materials of Au nanoparticle loaded ZnO nanowires (ZnO NWs) was successfully synthesized by electrostatic spinning and solution processing. Firstly, ZnO NWs were prepared by electrostatic spinning with polyvinylpyrrolidone (PVP) as a solvent. Afterwards, the prepared ZnO NWs were added to HAuCl4 aqueous solution with adjusted pH to load the Au nanoparticles onto them. Finally, the ZnO NWs were obtained with different sizes of Au nanoparticle loaded via annealing at different annealing temperatures. The X-ray diffraction (XRD) characterization indicates the good crystallinity and purity of the material, while transmission electron microscopy (TEM) images show the different sizes of Au nanoparticles on the ZnO NWs. The gas sensitivity test results show that all the Au-loaded ZnO NW samples show excellent gas sensitivity performance at a low operating temperature, and the loaded Au particles have an obvious influence on the sensing performance. A sensor loaded with large Au particles has a maximum response of 151.86 to 50 ppm ethanol at 200 °C, while a sensor loaded with small Au particles can respond to 50 ppm ethanol at 125 °C up to 108.22. Most importantly, the sensor shows high selectivity and long-term stability against a low concentration of ethanol. To interpret the gas-sensitivity mechanism of different responses under loadings of different Au particle sizes, the spillover effect of noble metal loads and the increase in the Schottky barrier due to the interaction of the noble metal with metal oxide semiconductor electrons are considered to explain the different sensor responses.
Herein, we report a successful approach for the vertically aligned ZnO nanorod arrays (ZNAs) deposited on fluorine-doped tin oxide (FTO) substrate by hydrothermal process. TiO2 nanoparticles were grown on the ZNAs by dip-coating. ZNAs and TiO2 nanoparticles (TNPs)-decorated ZNAs (TNPs@ZNAs) were used as a photoanode in dye-sensitized solar cells. The influence of bath temperature for the attainment of uniform decoration of TiO2 nanoparticles onto ZnO nanorod arrays and the photovoltaic performances of the assembled dye-sensitized solar cells were studied. The power conversion efficiency (PCE) of the TNPs@ZNAs arrays prepared at a bath temperature of 120 °C can reach 4.47%, representing better improvement when compared with ZNAs photoanode (3.15%).
The solar cells have been fabricated using cadmium sulfide (CdS) as a sensitizer by the chemical bath deposition (CBD) technique on the mesoporous TiO2 substrate. The different device configurations with titanium(IV) tetrachloride (TiCl4) treatment, TiO2 compact layer, with mesoporous TiO2 along with CdS sensitizer layer, were investigated. The CdS film morphology, optical properties, and crystalline structure of CdS film were studied. It was observed that TiCl4 treatment helped in reducing the recombination at the interfaces between conducting glass and TiO2 compact layer enabling higher carrier transport. Power conversion efficiency of 1.44% is achieved using a TiCl4 treatment on TiO2 compact layer with TiO2 mesoporous/CdS device under illumination of 100 mW/cm2.
Firstly, triarylmethanes bearing formyl groups (TRAM-CHOs) have been synthesized by the reaction of arenes with aromatic dialdehydes catalyzed by sulfuric acid immobilized on SiO 2 under solvent-free grinding conditions in good yields and short grinding time. Secondly, condensation of TRAM-CHOs with several arenes proceeded rapidly within a few minutes to afford the new corresponding mixed-bistriarylmethanes in excellent yields. TRAM-CHOs were also found to be valuable precursors for the Biginelli reaction to synthesize a variety of 3,4-dihydropyrimidin-2(1H)-one-triarylmethane hybrid derivatives. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Vertically aligned nanorods ZnO have been deposited hydrothermally on the pre-coated ZnO seeded-glass substrates. Enhanced vertical alignment is achieved as a result of combined film post-treatments. Dipped-drawn and immersed-washing the as-synthesized ZnO films in water as well as quenching of the hydrothermal were proposed to hinder excessive deposition and engineer the growth of ZnO nanorods. The XRD patterns shows suppressed growth of ZnO crystallite along (101) with increased textural coefficients on (002), TC 002 , from 3.94 to 5.23. Dense vertically aligned bundles of ZnO nanorods may reach up to 0.75 μm length. Bandgap energy of the resulted ZnO nanorod thin films were ranging from 3.69 to 3.79 eV, wider than those of bulk ZnO. Hydrothermal technique with simple post-treatments of immersed-washing and hydrothermal quenching has offered robust and efficient method to prepare vertically-aligned 1-D ZnO nanorods potential as photoanodes for dye-sensitized solar cells.
The present work reports the first demonstration of zirconium oxide (ZrO2) as a photoanode and rose bengal (RB) as a sensitizer. ZrO2 photoanode films were deposited on indium-doped tin oxide (ITO)-coated glass substrate by doctor blade technique. ZrO2 photoanodes were sensitized by rose bengal dye. Scanning electron microscopy (SEM) was applied to reveal the surface morphological changes for the RB-sensitized and unsensitized ZrO2 photoanodes. Using UV–vis spectrophotometer, optical absorption analyses were carried out for the RB-sensitized photoanodes. Platinum-coated ITO electrode was used as a counter electrode for electrons collection. The electron transfer at the interfaces was studied by electrochemical impedance spectroscopy. The device fabricated using the photoanode with dye loading time of 24 h performed better, it showed the photocurrent density (JSC), open-circuit voltage (VOC), and fill factor (FF) of about 0.01 mA/cm2, 258 mV, and 34%, respectively. Graphical abstract
In this work, high aspect ratio zinc oxide nanowires are synthesized using templated one-step electrodeposition technique. Electrodeposition of the nanowires is done using a handcrafted electronic system. Nuclear track-etched polycarbonate membrane is used as a template to form the high aspect ratio nanowires. The result of X-ray diffraction and scanning electron microscopy shows that nanowires with a good crystallinity and an aspect ratio of more than 30 can be achieved in a suitable condition. The height of electrodeposited nanowires reaches to about 11 μm. Based on the obtained results, high aspect ratio ZnO nanowires can be formed using inexpensive electrodeposition setup with an acceptable quality.
We describe the design and performance of a ZnO nanowire-based dye-sensitized solar cell. ZnO nanowires with a branched structure were employed as the wide-band-gap semiconductor to construct dye-sensitized solar cells which exhibit energy conversion efficiencies of 0.5% with internal quantum efficiencies of 70%. The nanowires provide a direct conduction path for electrons between the point of photogeneration and the conducting substrate and may offer improved electron transport compared to films of sintered nanoparticles. The devices have light harvesting efficiencies under 10%, indicating that current densities and efficiencies can be improved by an order of magnitude by increasing the nanowire surface area.
We explain the cause for the photocurrent and photovoltage in nanocrystalline, mesoporous dye-sensitized solar cells, in terms of the separation, recombination, and transport of electronic charge as well as in terms of electron energetics. On the basis of available experimental data, we confirm that the basic cause for the photovoltage is the change in the electron concentration in the nanocrystalline electron conductor that results from photoinduced charge injection from the dye. The maximum photovoltage is given by the difference in electron energies between the redox level and the bottom of the electron conductor's conduction band, rather than by any difference in electrical potential in the cell, in the dark. Charge separation occurs because of the energetic and entropic driving forces that exist at the dye/electron conductor interface, with charge transport aided by such driving forces at the electron conductor/contact interface. The mesoporosity and nanocrystallinity of the semiconductor are important not only because of the large amount of dye that can be adsorbed on the system's very large surface, but also for two additional reasons: (1) it allows the semiconductor small particles to become almost totally depleted upon immersion in the electrolyte (allowing for large photovoltages), and (2) the proximity of the electrolyte to all particles makes screening of injected electrons, and thus their transport, possible.
Excitonic solar cells-including organic, hybrid organic-inorganic and dye-sensitized cells (DSCs)-are promising devices for inexpensive, large-scale solar energy conversion. The DSC is currently the most efficient and stable excitonic photocell. Central to this device is a thick nanoparticle film that provides a large surface area for the adsorption of light-harvesting molecules. However, nanoparticle DSCs rely on trap-limited diffusion for electron transport, a slow mechanism that can limit device efficiency, especially at longer wavelengths. Here we introduce a version of the dye-sensitized cell in which the traditional nanoparticle film is replaced by a dense array of oriented, crystalline ZnO nanowires. The nanowire anode is synthesized by mild aqueous chemistry and features a surface area up to one-fifth as large as a nanoparticle cell. The direct electrical pathways provided by the nanowires ensure the rapid collection of carriers generated throughout the device, and a full Sun efficiency of 1.5% is demonstrated, limited primarily by the surface area of the nanowire array.
Recent developments in conjugated-polymer-based photovoltaic elements are reviewed. The photophysics of such photoactive devices is based on the photo-induced charge transfer from donor-type semiconducting conjugated polymers to acceptor-type conjugated polymers or acceptor molecules such as Buckminsterfullerene, C60. This photo-induced charge transfer is reversible, ultrafast (within 100 fs) with a quantum efficiency approaching unity, and the charge-separated state is metastable (up to milliseconds at 80 K). Being similar to the first steps in natural photosynthesis, this photo-induced electron transfer leads to a number of potentially interesting applications, which include sensitization of the photoconductivity and photovoltaic phenomena. Examples of photovoltaic architectures are presented and their potential in terrestrial solar energy conversion discussed. Recent progress in the realization of improved photovoltaic elements with 3 % power conversion efficiency is reported.
Recent developments in conjugated-polymer-based photovoltaic elements are reviewed. The photophysics of such photoactive devices is based on the photo-induced charge transfer from donor-type semiconducting conjugated polymers to acceptor-type conjugated polymers or acceptor molecules such as Buckminsterfullerene, C60. This photo-induced charge transfer is reversible, ultrafast (within 100 fs) with a quantum efficiency approaching unity, and the charge-separated state is metastable (up to milliseconds at 80 K). Being similar to the first steps in natural photosynthesis, this photo-induced electron transfer leads to a number of potentially interesting applications, which include sensitization of the photoconductivity and photovoltaic phenomena. Examples of photovoltaic architectures are presented and their potential in terrestrial solar energy conversion discussed. Recent progress in the realization of improved photovoltaic elements with 3 % power conversion efficiency is reported.
Recent developments in conjugated-polymer-based photovoltaic elements are reviewed. The photophysics of such photoactive devices is based on the photo-induced charge transfer from donor-type semiconducting conjugated polymers to acceptor-type conjugated polymers or acceptor molecules such as Buckminsterfullerene, C60. This photo-induced charge transfer is reversible, ultrafast (within 100 fs) with a quantum efficiency approaching unity, and the charge-separated state is metastable (up to milliseconds at 80 K). Being similar to the first steps in natural photosynthesis, this photo-induced electron transfer leads to a number of potentially interesting applications, which include sensitization of the photoconductivity and photovoltaic phenomena. Examples of photovoltaic architectures are presented and their potential in terrestrial solar energy conversion discussed. Recent progress in the realization of improved photovoltaic elements with 3 % power conversion efficiency is reported.
A novel technique has been developed to study the kinetics of the back reaction of electrons with I3- in dye-sensitized nanocrystalline cells. A solid-state switched operational amplifier feedback circuit controlling the cell is used to alternate open-circuit and short-circuit conditions. In the experiment, electrons are injected by the photoexcited dye during illumination at open circuit, and then the subsequent decay of the open-circuit photovoltage in the dark is recorded up to a given time, at which the cell is short-circuited abruptly. The electron charge extracted at short circuit is measured by a current amplifier and integrator device. The kinetics of electron decay at open circuit has been studied by varying the delay between interrupting the illumination and short-circuiting the cell. Analysis of the time dependence of the electron density has established that the decay process is second-order in the total electron concentration. This is consistent with a mechanism involving the formation of I2-• as an intermediate. The pseudo-second-order rate constant for the reaction of electrons with tri-iodide was found to be 1.9 × 10-17 cm3 s -1 for [I3-] = 0.05 M at 24 °C.
We have fabricated donor/acceptor-type organic photovoltaic devices based on copper phthalocyanine and Rose Bengal with varied number of donor/acceptor interfaces. Device architecture, namely, the number of such interfaces in the molecular scale, has been controlled via layer-by-layer electrostatic self-assembled film deposition technique. The interface area between donor and acceptor has been varied in order to optimize effective exciton separation and carrier transport. The number of donor/acceptor interfaces has opposite effects on exciton dissociation and charge transport in the devices. The results show that interface area has to be optimized to enhance the combined effect of exciton dissociation and carrier transport in organic photovoltaic devices.
TITANIUM oxide photocells, which are photochemically stable and decompose water into hydrogen and oxygen1,2, have a low efficiency3 and their spectral response is mostly in the ultraviolet, where the Sun's output is low. Other semiconductors such as cadmium sulphide or gallium phosphide, having smaller band gaps, are destroyed by light and their photocurrents deteriorate rather rapidly4. Photocurrents in dye sensitised photocells composed of aqueous electrolyte solutions and various semiconductor electrodes have also been studied5–7. All results obtained so far show that the dye sensitised photo-currents are very small, ~ 10−6–10−9 A cm−2, corresponding to a quantum efficiency ≲ 10−2. In this paper we report the successful construction of cells with a high power efficiency.
THE large-scale use of photovoltaic devices for electricity generation is prohibitively expensive at present: generation from existing commercial devices costs about ten times more than conventional methods1. Here we describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency. The device is based on a 10-µm-thick, optically transparent film of titanium dioxide particles a few nanometres in size, coated with a monolayer of a charge-transfer dye to sensitize the film for light harvesting. Because of the high surface area of the semiconductor film and the ideal spectral characteristics of the dye, the device harvests a high proportion of the incident solar energy flux (46%) and shows exceptionally high efficiencies for the conversion of incident photons to electrical current (more than 80%). The overall light-to-electric energy conversion yield is 7.1-7.9% in simulated solar light and 12% in diffuse daylight. The large current densities (greater than 12 mA cm-2) and exceptional stability (sustaining at least five million turnovers without decomposition), as well as the low cost, make practical applications feasible.
We have realized tuning of electronic memory-switching property via functional group modification in solid-state devices. Apart from their large ON/OFF ratio and long memory retention time, solid-state devices sustain repetitive switching between the two ON/OFF states at high frequencies. We have chosen several molecular systems with same backbone structure and tuned ON/OFF ratio from 4 to 300 000 simply by increasing the number of deactivating groups. A key to the large ON/OFF ratio in these devices has been the presence of acceptor groups in the molecules and consequently low OFF state current. We analyzed the appearance of ON state in terms of conjugation restoration of the molecules. A redox active group has been found to be necessary in the molecules for continuous flip-flop between “1” and “0” states for random access memory (RAM) applications.
Until now, photovoltaics--the conversion of sunlight to electrical power--has been dominated by solid-state junction devices, often made of silicon. But this dominance is now being challenged by the emergence of a new generation of photovoltaic cells, based, for example, on nanocrystalline materials and conducting polymer films. These offer the prospect of cheap fabrication together with other attractive features, such as flexibility. The phenomenal recent progress in fabricating and characterizing nanocrystalline materials has opened up whole new vistas of opportunity. Contrary to expectation, some of the new devices have strikingly high conversion efficiencies, which compete with those of conventional devices. Here I look into the historical background, and present status and development prospects for this new generation of photoelectrochemical cells.
A new and simple method was developed for synthesizing thin films of dye-modified ZnO by one-step cathodic electrodeposition from aqueous mixed solutions of zinc nitrate and sensitizing dyes. Electrochemical self-assembly of ZnO/eosin Y thin film was obtained using the same strategy. Surface adsorption of eosin Y hinders the crystal growth of ZnO, leading to the automatic formation of the desired porous structure of the film. Eosin Y molecules condense at sufficiently high concentration at the internal and external surfaces of the film to cause a specific intermolecular electronic interaction indicative of their ordered assembly.
Films with upright-standing zinc oxide nanosheet for use in dye-sensitized solar cells (DSC) were fabricated by overcoming the thermodynamic restriction. Layered hydroxide zinc carbonate (LHZC) sheets were grown perpendicular to the surface of a glass substrate starting from nucleation. The porous ZnO film fabricated by pyrolysis of the LHZC film was oriented to the c-axis parallel to the substrate. The DSC's prepared using these upright-standing ZnO nanosheet films exhibited a very high conversion efficiency of 3.9%, similar to the DSC made of ZnO electrodes, which is about the highest efficiency level of ZnO DSCs.
The influence of the organic layer thickness on short-circuit photocurrent spectra and efficiency is investigated in heterojunction photovoltaic cells with the electron donor materials polyp-phenylenevinylene PPV and Cu-phthalocyanine CuPc, respectively, together with C 60 as electron acceptor material. The main process of photocurrent generation after light absorption, exciton generation, and exciton diffusion in the bulk of the absorbing material is given by the exciton dissociation at the donor–acceptor interface. We determined a strong dependence of the optimum layer thickness of the absorbing material on the exciton diffusion length by systematically varying the layer thickness of the electron donor material. Additionally, a significant photocurrent contribution occurred due to light absorption and exciton generation in the C 60 layer with a subsequent hole transfer to PPV, respectively, CuPc at the dissociation interface. Using a simple rate equation for the exciton density we estimated the exciton diffusion lengths from the measured photocurrent spectra yielding 123 nm in PPV and 6820 nm in CuPc. By systematically varying the layer thickness of the C 60 layer we were able to investigate an optical interference effect due to a superposition of the incident with backreflected light from the Al electrode. Therefore both the layer thickness of the donor and of the acceptor layer significantly influence not only the photocurrent spectra but also the efficiencies of these heterolayer devices. With optimized donor and acceptor layer thicknesses power conversion efficiencies of about 0.5% under white light illumination were obtained. © 2001 American Institute of Physics.
A new series of panchromatic ruthenium(II) sensitizers derived from carboxylated terpyridyl complexes of tris-thiocyanato Ru(II) have been developed. Black dye containing different degrees of protonation [(C(2)H(5))(3)NH][Ru(H(3)tcterpy)(NCS)(3)] 1, [(C(4)H(9))(4)N](2)[Ru(H(2)tcterpy)(NCS)(3)] 2, [(C(4)H(9))(4)N](3)[Ru(Htcterpy)(NCS)(3)] 3, and [(C(4)H(9))(4)N](4)[Ru(tcterpy)(NCS)(3)] 4 (tcterpy = 4,4',4' '-tricarboxy-2,2':6',2' '-terpyridine) have been synthesized and fully characterized by UV-vis, emission, IR, Raman, NMR, cyclic voltammetry, and X-ray diffraction studies. The crystal structure of complex 2 confirms the presence of a Ru(II)N6 central core derived from the terpyridine ligand and three N-bonded thiocyanates. Intermolecular H-bonding between carboxylates on neighboring terpyridines gives rise to 2-D H-bonded arrays. The absorption and emission maxima of the black dye show a bathochromic shift with decreasing pH and exhibit pH-dependent excited-state lifetimes. The red-shift of the emission maxima is due to better pi-acceptor properties of the acid form that lowers the energy of the CT excited state. The low-energy metal-to-ligand charge-transfer absorption band showed marked solvatochromism due to the presence of thiocyanate ligands. The Ru(II)/(III) oxidation potential of the black dye and the ligand-based reduction potential shifted cathodically with decreasing number of protons and showed more reversible character. The adsorption of complex 3 from methoxyacetonitrile solution onto transparent TiO(2) films was interpreted by a Langmuir isotherm yielding an adsorption equilibrium constant, K(ads), of (1.0 +/- 0.3) x 10(5) M(-1). The amount of dye adsorbed at monolayer saturation was (n(alpha) = 6.9 +/- 0.3) x 10(-)(8) mol/mg of TiO(2), which is around 30% less than that of the cis-di(thiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) complex. The black dye, when anchored to nanocrystalline TiO(2) films achieves very efficient sensitization over the whole visible range extending into the near-IR region up to 920 nm, yielding over 80% incident photon-to-current efficiencies (IPCE). Solar cells containing the black dye were subjected to analysis by a photovoltaic calibration laboratory (NREL, U.S.A.) to determine their solar-to-electric conversion efficiency under standard AM 1.5 sunlight. A short circuit photocurrent density obtained was 20.5 mA/cm(2), and the open circuit voltage was 0.72 V corresponding to an overall conversion efficiency of 10.4%.
We demonstrate that semiconductor nanorods can be used to fabricate readily processed and efficient hybrid solar cells together with polymers. By controlling nanorod length, we can change the distance on which electrons are transported directly through the thin film device. Tuning the band gap by altering the nanorod radius enabled us to optimize the overlap between the absorption spectrum of the cell and the solar emission spectrum. A photovoltaic device consisting of 7-nanometer by 60-nanometer CdSe nanorods and the conjugated polymer poly-3(hexylthiophene) was assembled from solution with an external quantum efficiency of over 54% and a monochromatic power conversion efficiency of 6.9% under 0.1 milliwatt per square centimeter illumination at 515 nanometers. Under Air Mass (A.M.) 1.5 Global solar conditions, we obtained a power conversion efficiency of 1.7%.
A method for growing vertical ZnO nanowire arrays on arbitrary substrates using either gas-phase or solution-phase approaches is presented. A approximately 10 nm-thick layer of textured ZnO nanocrystals with their c axes normal to the substrate is formed by the decomposition of zinc acetate at 200-350 degrees C to provide nucleation sites for vertical nanowire growth. The nanorod arrays made in solution have a rod diameter, length, density, and orientation desirable for use in ordered nanorod-polymer solar cells.
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