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(a) Band diagram of 0% cobalt doped ZnO/CuO heterojunction solar cells. (b) Schematic band offsets in 0–20% cobalt doped ZnO/CuO heterojunction. VBM and CBM values are from the Fermi level
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In this study, we investigated the effect of cobalt doping on band alignment and the performance of nanostructured ZnO/CuO heterojunction solar cells. ZnO nanorods and CuO nanostructures were fabricated by a low-temperature and cost-effective chemical bath deposition technique. The band offsets between Zn1−xCoxO (x = 0, 0.05, 0.10, 0.15, and 0.20)...
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The effect of six different substrate-inclined angle with the vessel on the characteristics properties of the Zinc Oxide (ZnO) nanorods was explored and reported. The vertically well-aligned ZnO Nanorods (NRs) were synthesized on glass substrates by using the low-cost chemical bath deposition (CBD) method at 90 °C. The RF magnetron sputtering has b...
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... Furthermore, the reduced bandgap facilitates the design of ZnObased devices with tailored optical and electronic properties, enabling their integration into a wider range of optoelectronic systems [18][19][20][21][22][23]. Overall, the transition from wide bandgap to narrow bandgap ZnO represents a significant advancement in materials science, with promising implications for the development of more efficient solar cells and other optoelectronic devices [24][25][26][27]. ...
This present study devoted to systematic synthesis and investigation of zinc oxide (ZnO) nanoparticles with a precisely tailored band gap of 1.4 eV, aiming to their suitability for high-sensitivity photoelectrochemical (PEC) detection. The reaction conditions were optimised in order to get ZnO nanoparticles with narrow band gap and predominantly in the form of 2D nanosheets, exhibiting intriguing properties attributable to their narrow band gap. Structural analysis carried out by using X-ray diffraction (XRD) confirmed the formation of pure ZnO in the wurtzite phase at specific precursor concentrations. It was observed by UV-vis spectroscopy that as the time duration between synthesis of the sample and its annealing was increased from 0, 15, 30 to 60 days, the band gap reduces from 2.8 to 1.4 eV. Microstructural and morphological analysis by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) elucidated the formation of well-defined 2D nanosheets of ZnO. Further characterization utilizing techniques such as thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and photoluminescence (PL) spectroscopy ensured the formation of pure ZnO phase with absence of impurities and provided insights into the band structure of the synthesized ZnO nanoparticles. Electrochemical properties were evaluated using cyclic voltammetry (CV) and potentio electrochemical impedance spectroscopy (PEIS) techniques in both dark and light conditions, revealing enhanced performance attributed to the optimized band gap. Additionally, the photoelectrochemical detection capabilities of the synthesized ZnO nanoparticles were thoroughly assessed, demonstrating their remarkable sensitivity and stability. This comprehensive investigation highlights the significance of tailoring the band gap of ZnO nanoparticles for advancement in photoelectrochemical detection technologies.
... Among several kinds of metal oxide, thin films of CuO have drawn attention for possible applications in energy storage and solar cells as active layers, as well as their utilization as passive layers in solar selective surfaces [1]. Copper oxide thin films, comprising stable oxides such as cupric oxide, CuO (band gap of 1.2-1.9 ...
Here, pure, and Nd-doped CuO thin films with different composition (0.5 mol%, 1 mol%, 3 mol% and 5 mol%) were prepared following sol-gel spin coating route. X-ray diffraction analysis exhibited polycrystalline monoclinic structure of the films. Crystallite size and micro-strain were calculated from XRD analysis. As Nd doping was increased, crystallite size decreased for any addition beyond 0.5 mol%. Micro-Strain was also increased with increasing Nd doping indicating the lattice misfit because of size difference of Cu2+ and Nd3+. Optical properties of the pristine and Nd doped films were characterized using UV–visible spectrophotometry. The bandgap values were 1.92, 1.90, 1.87, 2.02 and 1.97eV for undoped, 0.5 mol%, 1 mol%, 3 mol% and 5 mol% Nd doped films, respectively. Various optical parameters and dielectric constants were calculated for various optoelectronic applications. The topography of the films was studied using Atomic Force Microscopy and it revealed that the average roughness of the films varied in the range of 4.9–8.1 nm. Electrical conductivity of the undoped film was increased from 0.315 to 0.596 S/cm for 5 mol% Nd doping which was measured using a 4-point probe method. Hall measurements showed an increment of carrier concentration by an order of 10 for the 5 mol % Nd doping compared to undoped CuO thin film, where charge carrier mobility was also increased from 0.102 to 0.453 cm^2/Vs. However, for the maximum doping concentration of 5 mol%, the films remained p-type semiconductor confirmed by the positive value of the co-efficient RH.
... The high values of n are consistent with the high value of 13 reported by Hussain et al. 44 Furthermore, the present results are more realistic than the value of 21.3 reported by Zainelabdin et al. 45 The high values obtained for I S indicate the presence of significant recombination at the interface. 8,46 The decrease in I S with the incorporation of 1.5% Sn doping may be due to the increased b . 46 Figure 5 indicates that all junctions exhibit leakage current in the dark to variable degrees. ...
... 8,46 The decrease in I S with the incorporation of 1.5% Sn doping may be due to the increased b . 46 Figure 5 indicates that all junctions exhibit leakage current in the dark to variable degrees. Under dark conditions, no J SC values are zero for any junctions, whereas under illumination, all junctions exhibit short-circuit photocurrents. ...
Heterojunctions based on p-CuO/n-ZnO, prepared by simple methods such as spin coating, normally exhibit low photoconversion efficiency and require modification. Doping the ZnO layer with ions such as Sn4+ could be a solution. In this work, heterojunctions were prepared by two simple methods. In method 1, to prepare the CuO@ZnO junction, the n-ZnO layer was spin-coated on tin-doped indium oxide/glass substrates (ITO/glass) followed by spin coating of the p-CuO layer. In method 2, to prepare the ZnO@CuO/Cu sheet junction, the p-CuO layer was prepared by thermal oxidation of the Cu metal sheet, followed by spin coating of ZnO. In both cases, the ZnO film was doped with Sn4+ ions at 1.5% concentration by mole. The effects of Sn-doping on the structural and morphological properties of the junction were comparatively studied by X-ray diffraction and atomic force microscopy. In both preparations, doping affected the optical, electrical and photovoltaic (PV) properties. The preparation method also affected junction characteristics, as preparation method 2 showed heterojunctions with higher PV characteristics. The results show inroads to improving PV characteristics for the heterojunction based on the proper preparation method and Sn doping.
... Copper has two stable oxidation states: Cu + and Cu 2+ and the presence of shakeup peaks in the higher binding energy region is a clear indication of +2 oxidation state of Cu. 42 Satellite peaks are characteristics of the materials having d 9 conguration in the ground state. 43 The two shake up peaks at 940.84 and 943.16 eV arise due to the multiplet splitting in 2p 5 3d 9 conguration. 44 These satellite peaks are not observed in the Cu + conguration as the completely lled d 10 conguration does not allow screening via charge transfer to the d states. ...
Doping is one of the easiest methods to enhance the properties of semiconducting thin films. This work presents a systematic study of the influence of Mg doping on the optoelectronic properties of copper oxide (CuO) thin films prepared by spray pyrolysis. The pristine and doped films were prepared on glass substrates at an optimized temperature of 350 °C and a precursor solution concentration of 0.15 M while the Mg doping concentration was varied between 2 and 10 at%. The properties of the prepared films were studied in detail by using various characterization techniques such as X-ray diffraction, field emission scanning electron microscopy, Raman and photoluminescence, X-ray photoelectron spectroscopy and Hall measurement. The results suggest that oxygen interstitial (Oi) defects were enhanced upon doping which has influenced the properties of the film. The size of the crystallites reduced, and the band gap widened after doping. In addition, comprehensive density functional theory analyses have been conducted to gain a thorough understanding of the impact of impurity (i.e., doping/interstitial) atoms on the optical and electrical characteristics of CuO. This study shows that Oi defects improved the conductivity and enhanced the carrier concentration leading to an improvement in the electrical properties of the films.
... Finally, samples were rinsed with deionized water, dried in the air, and annealed at 300 • C for an hour in the air. The details result and analysis of CuO thin films were reported in our previous work [21]. ...
... This is due to the Constant Phase Element (CPE1) charge accumulation at the interface whereas the small semicircle in the region of low-frequency is ascribed to the recombination resistance (R3). In addition, the capacitance (Constant Phase Element: CPE2) corresponds to electron-hole recombination [21]. It was observed that the interfacial charge transfer resistance (R2) is obtained decreased with increased concentration of Al from 0 to 3 mol%. ...
... eV, and 2.0-4.0 eV, respectively [7,8]. Alternatively, zinc oxide (ZnO) is a wide bandgap (3.3 eV) semiconductor with natural n-type conductivity, which can be efficiently utilized as an ultra-violet light absorber [9]. Consequently, integration of CuO and ZnO on the same Si-platform may be advantageous for fabricating highly efficient photovoltaic devices capable of absorbing the UV to NIR region (350-1100 nm) of the incident solar spectrum. ...
... The lower value of dark reverse leakage current in CuO:Zn/n-Si heterojunction may be attributed to the suppression of non-radiative recombination and lower interfacial defects. Also, the relatively smaller value of n for the CuO:Zn/n-Si device, in comparison with CuO/n-Si heterojunction suggests the reduction of interfacial recombination and dwindling of defect activities which could be due to the increased built-in potential (as estimated from C-V analysis) and better interfacial quality of the device [9]. Figure 8b depicts the J-V curve of the Si-based CuO:Zn and CuO thin film heterojunction diodes under 1000 W/m 2 intensity of incident wavelength (AM1.5G). ...
In the current study, Zn-incorporated CuO (CuO:Zn) and pure CuO thin film heterojunction devices have been fabricated on n-Si (⟨100⟩\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\langle 100\rangle$$\end{document}) substrate, applying vapor–liquid–solid (VLS), for their potential application as photovoltaic devices. The uniformity of the thin films on Si-substrate and their crystalline orientation are verified using FESEM images and XRD studies, respectively. EDS and XPS measurements analyze the chemical stoichiometry and valance states of the as-grown oxides. The influence of incorporating Zn atoms on the structural stabilities of Zn-incorporated CuO was further studied using the DFT (density functional theory) simulation. From spectroscopic ellipsometry measurement, the direct energy bandgaps of CuO:Zn and CuO thin films are assessed to be 2.26 eV and 2.05 eV, respectively. Further, the electronic properties of such heterojunctions are investigated from the junction current–voltage and capacitance–voltage characteristics. The comparative photovoltaic study of CuO:Zn and CuO films suggests that the introduction of Zn into the CuO matrix enhances the power conservation efficiency (PCE %) and external quantum efficiency (EQE%) by almost 2 times. Also, a high spectral responsivity (~ 0.30 A/W @ 0 V) as well as detectivity (1.96 × 10¹² cm Hz1/2/W @ 0 V) have been achieved for the CuO:Zn/n-Si photodetector. Therefore, the incorporation of ZnO into the CuO lattices by employing the cost-effective VLS mechanism suggests a significant improvement of optoelectronic and photovoltaic properties of such films for the fabrication of future devices.
... It is interesting to note that both oxides under consideration also have piezoelectric properties, meaning that they can generate electrical charge when mechanically deformed [22]. Thus, both 1D and 2D structures of copper and zinc oxides have special properties that determine their potential use in various applications and make them valuable materials for a variety of innovative applications [23][24][25]. ...
The most effective methods for the synthesis of nanostructured copper and zinc oxides, which have unique properties and potential applications in a variety of fields including electronics, photonics, sensorics, and energy conversion, are analyzed. Special attention is paid to laser-based methods for synthesizing oxide nanostructures, with an emphasis on the importance of controlling power density distribution to influence the quality and properties of the nanomaterials. The great significance of wavefront shaping techniques for controlling laser-initiated processes is highlighted, which enable precise control over the phase and amplitude of light waves to achieve desired outcomes in optics and laser-assisted formation of one- and two-dimensional structures of oxide semiconductor materials. Diffractive computer optics is presented as a powerful tool for precise beam control. The significance of laser-induced thermochemical processes for creating and improving the properties of ZnO and CuO-based nanomaterials is discussed. The presented analysis shows that the synthesis of nanocomposites based on ZnO and CuO using pulse-periodic laser treatment, coupled with precise laser beam control using free-form diffractive optics, presents novel opportunities for applications in optoelectronics, sensor technology, electronics and portable energy sources manufacturing, and various other fields.
... Among them, the doping process is considered to be a potential strategy for enhancing the optical and electrical characteristics of these metal-oxide nanostructures. For example, cobalt (Co) is considered as a great dopant in ZnO NRs for adjusting optical and electrical characteristics due to its a relatively higher solubility limit than other kinds of dopants, including Mg, Cs, Li and Al [79]. In a recent study, the effect of Co doping on band alignment and the performance of nanostructured ZnO/CuO heterojunction solar cells has been reported [79]. ...
... For example, cobalt (Co) is considered as a great dopant in ZnO NRs for adjusting optical and electrical characteristics due to its a relatively higher solubility limit than other kinds of dopants, including Mg, Cs, Li and Al [79]. In a recent study, the effect of Co doping on band alignment and the performance of nanostructured ZnO/CuO heterojunction solar cells has been reported [79]. By modifying conduction and valence band offsets with cobalt doped ZnO NRs, the efficiency of ZnO/ CuO solar cells was shown to be improved. ...
In recent years, one-dimensional (1D) nanostructures, including nanorods, nanowires and nanotubes have been receiving a great deal of research attention due to their special and outstanding many characteristics that play a very important role in the manufacture of high-performance devices, including photodetectors, solar cells, light emitting diodes and power nano-generators, with novel functionalities. To date, a number of materials have been employed in the production of 1D structures for the fabrication of high-performance electronic and opto-electronic devices. Due to its stability, high conductivity, high electron affinity, and outstanding electron mobility, zinc oxide (ZnO) stands out among the others as a material that is particularly appealing to be employed in a variety of opto-electronic device applications. In this review article, we provide a brief overview of the most recent advances in popular synthesis methods and photovoltaic applications of 1D ZnO nanostructures, including our own recent studies. In particular, a special focus is given on the progress in 1D ZnO nanostructures based inorganic solar cells. Future research opportunities and challenges for solar cells based on 1D ZnO nanostructures are also highlighted.
... The dependence of Im(Z) = X on Re(Z) = R, or the dependence of Re(Y)/ω = G/ω on Im(Y)/ω = C are called Nyquist or Cole-Cole plots. [28][29][30] In Fig. 6 the dependence of G/ω on C is presented for the Ni/ ZnO/n-Si heterostructure with a 135-nm-thick ZnO layer. Different curves correspond to gate voltages varying from − 0.5 V to 0.5 V with the step of 0.2 V. From these complex impedance plots, the effective carrier lifetime can be estimated, because the highest point of the semicircle in the Cole-Cole plot corresponds to a characteristic carrier recharging frequency, the reciprocal of which is the effective carrier lifetime. ...
The results of electrical and photoelectrical characterization of the interface and bulk properties of n ⁺ -ZnO/ n -Si and poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/ n ⁺ -ZnO/ n -Si heterostructures are presented. It was found that the PEDOT:PSS layer deposited on the surface of zinc oxide increases the potential barrier at the ZnO/Si interface, leading to higher band bending in the silicon, which is important for solar cell applications. The recombination rate at the interface decreases because of the creation of an inversion layer in the silicon under operational conditions. The increase of the potential barrier in PEDOT:PSS/ n ⁺ -ZnO/ n -Si heterostructures results in the increase of the open-circuit voltage by 54–180%. The external quantum efficiency in PEDOT:PSS/ n ⁺ -ZnO/ n -Si heterostructures increases by 100% at 450 nm.
... In this equivalent circuit, the constant phase elements (CPE) indicated by Q a , Q b which are associated for the deviation of the capacitance from the actual value. This leaky capacitance nature in the system is arising due to various factors like surface defects, porosity, and surface roughness [35]. ...
A bilayer heterojunction consisting of p-NiO/Zn(1-x)Sn(x)O (TZO) (x = 0.14) was grown via DC magnetron
sputtering and the impact of Rapid Thermal Annealing (RTA) on its physical properties was evaluated. Structural, morphological, optical, and electrical analyses were performed to analyze the effects of RTA on the heterojunction. X-ray diffraction analysis confirmed the polycrystalline nature of both layers and scanning electron
microscopy imaging depict the absence of cracks and pinholes in the grown layers. RTA treatment resulted in an
increase in the visible region transmittance of the NiO/TZO heterojunction and a sharp absorption edge in the
ultraviolet region was observed from the optical studies. Electrical properties such as rectification ratio, ideality
factor, barrier height, and built-in potential were determined through dark current-voltage and capacitance voltage measurements, which showed improvement in rectification ratio and barrier height after RTA. Impedance spectroscopy revealed a decrease in series resistance after RTA. These results contribute to the development
of high-performance metal oxide-based heterojunction for next-generation photonic and electronic devices.
