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The detailed energy-level diagram and corresponding upconversion process of a hexagonal β-NaYF4:Yb³⁺, Er³⁺ nanoparticle.
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Organic-inorganic lead halide based perovskite solar cells have received broad interest due to their merits of low fabrication cost, a low temperature solution process, and high energy conversion efficiencies. Rare-earth (RE) ion doped nanomaterials can be used in perovskite solar cells to expand the range of absorption spectra and improve the stab...
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Extended efficiency of solar cells to ensemble more solar energy as well as its optimum conversion and utilization is believed to be a major challenge in current times. The spectral mismatch between the distribution of energy in the solar spectrum incidence and the semiconducting material band gap is a major restriction in the performance of solar...
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... In the last decade, upconversion (UC) photoluminescence (PL) materials have gained increasing attention for their ability to absorb multiple low-energy long-wave radiations, to achieve the infrared to visible light conversion [1][2][3][4][5]. Among the reported materials, rare earth doped UC compounds have the advantages of high luminescence efficiency. ...
β-NaYF4: Yb3+/Tm3+/Zr4+ microcrystals are synthesized by a facile hydrothermal
route. The up-conversion (UC) luminescence and photoelectric effects are enhanced
simultaneously with the introduction of Zr4+ ions under IR excitation. With the Tm3+ ions
fluorescence spectra under 980 nm excitation, the blue and red emissions reached the highest
intensity in the case of 4 mol% Zr4+ doping. Taking the advantage of Zr4+ stimulates the free
electrons transfer from the valence band (VB) to the conduction band (CB) in β-NaYF4:Yb3+/Tm3+/Zr4+ microcrystals, the photocurrent reached the highest intensity in the
case of 4 mol% Zr4+ doping at 780 nm excitation. The β-NaYF4: Yb3+/Tm3+/Zr4+
microcrystals with both enhanced UC luminescence and photoelectric properties are highly
potential to contribute in photovoltaic and infrared sensors application.
... Converting long wavelength light into short wavelength light, up-conversion (UC) luminescence involves the unique anti Stokes physical process. [1][2][3][4][5] UC materials have several significant applications including bioimaging, 6 solar cells, 7 optical sensing 8 and temperature measurements. 9 In recent years, non-contact temperature measurements using rare-earth luminescent materials have attracted considerable attention. ...
Oxides are physically and chemically stable. Non-contact thermometer-Yb3+-Er3+ ions co-doped solid solution (Y0.5In0.5)2O3, is prepared by the regular solid method. The structural results obtained by XRD indicate that a pure phase solid solution (Y0.5In0.5)2O3 has been obtained. The solid solution (Y0.5In0.5)2O3 has a similar crystal structure, especially Y2O3 and In2O3 with the same space group (Ia3̄). Green emission from 500 to 600 nm is due to Er3+ 4f-4f transitions: 4S3/2 → 4I15/2 at 567 nm and 2H11/2 → 4I15/2 at 528 nm. Red emissions from 630 to 720 nm are attributed to Er3+: 4F9/2 → 4I15/2. UC luminescence changes greatly with laser diode power and Er3+ and Yb3+ content. Furthermore, the two-photon process is confirmed to be dominant between Yb3+ and Er3+ in oxide solid solution (Y0.5In0.5)2O3. Optical temperature sensitivity is also investigated systematically in order to explore the application of the oxide solid solution (Y0.5In0.5)2O3. The temperature-dependent green fluorescence at 528 and 567 nm was investigated with the range of 313-573 K. 0.316% K-1 is the maximum absolute sensitivity at 503 K, which is higher than most Yb3+/Er3+ co-doped systems. In addition, the solid solution (Y0.5In0.5)2O3:Yb3+,Er3+ has better thermal stability and stronger UC emission than a simple substance with excellent temperature sensing performance. It indicates that Yb3+-Er3+ ions co-doped (Y0.5In0.5)2O3 solid solution is a good candidate for optical temperature sensing.
... At present, the traditional fossil fuels with limited reserves are still the main source of energy for human beings, but the burning of fossil fuels has caused serious environmental pollution and greenhouse effects [4][5][6][7]. With the rapid development of global industrialization, environmental pollution and energy shortages are two major problems facing the current world [8,9]. Therefore, searching for renewable energy with reduced carbon emissions, secure long-term energy supply, and less dependence on fossil fuels is mandatory for the sustainable development of the world [10,11]. ...
Triboelectric nanogenerator (TENG) can convert tiny mechanical energy into precious electrical energy. Constant improvements to the output performance of TENG is not only the driving force for its sustainable development, but also the key to expand its practical applicability in modern smart devices. However, most previous studies were conducted at room temperature, ignoring the influence of temperature on the output performance of TENG. Additionally, due to thermionic emission effect, the electrons transferred to a dielectric surface can be released into a vacuum after contact electrification. Therefore, TENG cannot maintain an effective electrical output under high-temperature conditions. Here, a series of high-temperature operatable flexible TENGs (HO-TENGs) based on nanofiber/microsphere hybrid membranes (FSHMs) was fabricated by electrospinning and electrospraying. The Voc of HO-TENG is 212 V, which is 2.33 times higher than that of control TENG. After 10,000 cycle stability tests, the HO-TENG shows excellent durability. Especially, this HO-TENG can maintain 77% electrical output at 70 °C compared to room temperature, showing excellent high-temperature operability. This study can not only provide a reference for the construction of advanced high-performance TENG, but also provide a certain experimental basis for efficient collection of mechanical energy in high-temperature environment and promote the application of TENG devices in harsh environments.
... The energy crisis and greenhouse gas emissions are the most crucial worldwide problems nowadays, which are mainly caused by the low efficiency and excessive consumption of nonrenewable fossil fuels [1,2]. Thus, the utilization of renewable energies and the development of relevant energy conversion technologies are highly urgent and essential [3][4][5][6][7]. Among various types of renewable energies/sources, solar energy has gained particular interest due to its inexhaustible and clean nature, which can be efficiently utilized by three main routes: photovoltaic cells, photocatalysis and solar-thermal power generation [1,[8][9][10]. ...
Organic–inorganic perovskite solar cells (PSCs) have delivered the highest power conversion efficiency (PCE) of 25.7% currently, but they are unfortunately limited by several key issues, such as inferior humid and thermal stability, significantly retarding their widespread application. To tackle the instability issue, all-inorganic PSCs have attracted increasing interest due to superior structural, humid and high-temperature stability to their organic–inorganic counterparts. Nevertheless, all-inorganic PSCs with typical CsPbIBr2 perovskite as light absorbers suffer from much inferior PCEs to those of organic–inorganic PSCs. Functional doping is regarded as a simple and useful strategy to improve the PCEs of CsPbIBr2-based all-inorganic PSCs. Herein, we report a monovalent copper cation (Cu+)-doping strategy to boost the performance of CsPbIBr2-based PSCs by increasing the grain sizes and improving the CsPbIBr2 film quality, reducing the defect density, inhibiting the carrier recombination and constructing proper energy level alignment. Consequently, the device with optimized Cu+-doping concentration generates a much better PCE of 9.11% than the pristine cell (7.24%). Moreover, the Cu+ doping also remarkably enhances the humid and thermal durability of CsPbIBr2-based PSCs with suppressed hysteresis. The current study provides a simple and useful strategy to enhance the PCE and the durability of CsPbIBr2-based PSCs, which can promote the practical application of perovskite photovoltaics.
... Alternatively, it is possible to introduce RE-containing DS/DC and UC layers into the devices to harvest the UV and NIR photons in the AM 1.5 G solar irradiance spectrum and reemit visible light. This has been demonstrated to be an effective method of generating extra photocurrent and breaking the inherent conversion efficiency limitation of solar cells [54][55][56]. As a bonus, the extra DS/DC/UC layers on the transparent conductive oxide (TCO) layer of the devices are also expected to promote light-harvesting efficiency by increasing the scattering of photons [57,58]. ...
... As a class of elements with unique properties, the use of RE elements in optoelectronic devices has explicitly been reviewed by several groups. For example, Qiao et al. reviewed the recent progress of RE-doped nanomaterials in electrodes, active layers, and external functional layers in PSCs [55]. A year later, Rajeswari et al. thoroughly summarized the applications of various RE-based DC/UC materials for dye-sensitized solar cells (DSSCs) and PSCs, focusing on light harvesting, light-scattering, and stability improvement [6]. ...
Metal-halide perovskites-based optoelectronic devices, such as solar cells and light-emitting diodes (LEDs), are transitioning from promising performers to direct competitors to well-established technologies due to the advantage of cost-effectiveness. Perovskite solar cells (PSCs) have achieved power conversion efficiency beyond 25% in less than ten years, showing great potential in low-cost photovoltaics with high efficiency and low fabrication cost. Nanostructured perovskites have yielded world-record LEDs due to their high versatility in the local management of charge carriers and the close-to-unit photoluminescence quantum yields (PLQY). However, the development of such perovskite optoelectronic devices is still restricted by their narrow light absorption band, low charge carrier mobility, energy level mismatching, and poor stability and lifespan of the devices. Lanthanides have been applied in perovskite optoelectronic devices to minimize the abovementioned shortcomings. Herein, we provide a brief review of the history of lanthanide materials in perovskite optoelectronic devices and a detailed discussion of the recent developments in this field. We will focus on the advances in lanthanide-doped downshifting downconversion, upconversion systems, perovskite light-harvesters, and charge transport layers for both PSCs and lanthanides-doped perovskite quantum dots/nanocrystals (QDs/NCs) for photoluminescent devices.
... At present, photovoltaic modules based on wafer-based crystalline silicon solar cells account for >90% of the global photovoltaic market [1][2][3][4][5]. Laudable enhancements in power conversion efficiency (η) have been experienced for this technology over the last few years, leading to thin film, tandem, and various lab-based architectures [6][7][8][9][10][11][12][13]. Additionally, the manufacturing process of crystalline-based solar modules requires expensive materials and high production costs. ...
The nitrogenated holey two-dimensional carbon nitride (C2N) has been efficaciously utilized in the fabrication of transistors, sensors, and batteries in recent years, but lacks application in the photovoltaic industry. The C2N possesses favorable optoelectronic properties. To investigate its potential feasibility for solar cells (as either an absorber layer/interface layer), we foremost detailed the numerical modeling of the double-absorber-layer–methyl ammonium lead iodide (CH3NH3PbI3) –carbon nitride (C2N) layer solar cell and subsequently provided in-depth insight into the active-layer-associated recombination losses limiting the efficiency (η) of the solar cell. Under the recombination kinetics phenomena, we explored the influence of radiative recombination, Auger recombination, Shockley Read Hall recombination, the energy distribution of defects, Band Tail recombination (Hoping Model), Gaussian distribution, and metastable defect states, including single-donor (0/+), single-acceptor (−/0), double-donor (0/+/2+), double-acceptor (2/−/0−), and the interface-layer defects on the output characteristics of the solar cell. Setting the defect (or trap) density to 1015cm−3 with a uniform energy distribution of defects for all layers, we achieved an η of 24.16%. A considerable enhancement in power-conversion efficiency ( η~27%) was perceived as we reduced the trap density to 1014cm−3 for the absorber layers. Furthermore, it was observed that, for the absorber layer with double-donor defect states, the active layer should be carefully synthesized to reduce crystal-order defects to keep the total defect density as low as 1017cm−3 to achieve efficient device characteristics.
... At present, photovoltaic modules based on wafer-based crystalline silicon solar cells account for >90% of the global photovoltaic market [1][2][3][4][5]. Laudable enhancements in power conversion efficiency (η) have been experienced for this technology over the last few years, leading to thin film, tandem, and various lab-based architectures [6][7][8][9][10][11][12][13]. Additionally, the manufacturing process of crystalline-based solar modules requires expensive materials and high production costs. ...
Herein we foremost detailed the numerical modeling of the double absorber layer- methyl ammonium lead iodide– carbon nitride layer solar cell and subsequently provided in-depth insight on the active layer associated with dominant radiative and non-radiative recombination losses limiting the efficiency ( ) of the solar cell. Under recombination kinetics phenomena, we explored the influence of Radiative recombination, Auger recombination, Shockley Read Hall recombination, the energy distribution of defects; Band Tail recombination (Hoping Model), Gaussian distribution, metastable defect states including single donor (0/+), single acceptor (-/0), Double Donor (0/+/2+), double acceptor (2/-/0-), and the interface layer defects on the output characteristics of the solar cell. Setting defect (or trap) density to with uniform energy distribution of defects for all the layers, we achieved the of 24. 16 %. A considerable enhancement in power conversion efficiency was perceived as we reduced the trap density to for the absorber layers. Further, it was observed that for the absorber layer with double donor defect states, the active layer should be carefully synthesized to reduce crystal order defects to keep the total defect density as low as to achieve efficient device characteristics
... TiO 2 has a band-gap value of ~3.2 eV, making it photoactive in the ultraviolet (UV) spectrum of electromagnetic energy, which accounts for just 5% of solar radiation and on the other hand, has poor photon absorption and electrical conductivities. However, metal doping has attracted a lot of attention because of an effective way to change the conductivity, electrical, and optical properties of an n-type layer [14][15][16][17][18][19]. The insertion of holmium (Ho 3+ ) rare-earth ions into TiO 2 modifies its conductivity and shifts its absorption to visible and near-infrared wavelengths. ...
Titanium dioxide (TiO2) and holmium (1.2 mol% Ho³⁺) doped TiO2 nanoparticles were synthesized via sol-gel method using polyvinylpyrrolidone (PVP) co-polymer as a pore forming agent. The nanoparticles were dispersed in a solvent and drop-cast on a glass substrate to make films. The films were then calcined at 550 °C for 4 h in a pre-heated muffle furnace. Methylammonium lead iodide (MAPbI3) was incorporated with TiO2 and TiO2:Ho³⁺ nanoparticles. Therefore, the samples TiO2, TiO2:Ho³⁺, TiO2:MAPbI3 and TiO2:Ho³⁺:MAPbI3 were obtained and their properties as an electron transporting and photon absorption layers, respectively, were evaluated for possible application in perovskite solar cells. XRD results revealed a rutile phase which was found to be consistent with the RAMAN analysis. FESEM showed spherical nanoparticles with irregular pore size for TiO2 and TiO2:Ho³⁺ samples, whereas MAPbI3 nanocrystals seemed to have filled-up the pores in TiO2:MAPbI3 and TiO2:Ho³⁺:MAPbI3 samples. UV–Vis results showed an expected UV absorption of TiO2 with the absorption band at ∼366 nm and upon doping with 1.2 mol% of Ho³⁺ ions, an improved absorption and a shift towards the visible region was observed. Small absorption bands at ∼453, 541 and 645 nm were detected, which are resulting from the Ho³⁺ transitions. When MAPbI3 was incorporated with TiO2:Ho³⁺, absorption in the visible range remained improved with the bands at ∼541 and 645 becoming intense. TiO2:MAPbI3 sample showed a further absorption improvement with a red-shift of the absorption band. The band gap energy was estimated and found to be ∼3.00, 2.35, 2.32 and 2.34 eV for TiO2, TiO2:Ho³⁺, TiO2:MAPbI3 and TiO2:Ho³⁺:MAPbI3, respectively. The red-shift and the reduction of the bandgap values is a good indication that these materials will absorb as much photons in the visible and near-infrared regions. The current-voltage (I–V) analysis revealed that the sample TiO2:MAPbI3 have higher current flow, implying lower resistance in the material. The PL results indicated low electron-hole recombination as the intensity was considerably decreased upon doping with Ho³⁺ and incorporating MAPbI3.
... Though photovoltaic cells made from crystalline and amorphous silicon are common, devices are being designed and constructed by using mesoscopic, inorganic, or organic semiconductors. Besides, ion-doped up-conversion (UC) photovoltaic (PVT) cells are promising to overcome the efficiency-limit of the available solar cells, both theoretically and practically (Qiao et al. 2018). Interestingly, in Asian countries like Malaysia, Turkey etc., energy generated from biomass has been reported to contribute significantly in improving the economic condition of the nations, in addition to largely meeting their energy demand (Ozturk et al. 2017). ...
Energy crisis is a matter of serious global concern as the depleting energy sources exert a deleterious effect on the economy. Additionally, the existing sources of energy are brimming with deleterious side effects on human health and the environment. Hence, a global effort is being made for the utilization of green chemistry for sustainable energy applications and for curbing the degradation of environment associated with the use of large-scale energy devices, and thermoelectric vehicles. Green chemistry, coupled with nanotechnology, offers a technological innovation in the domain of energy sources and subsequent energy conversion. Nanostructuring of energy-active materials notably enhances the performance of the devices due to enhancement in specific surface area, increased number of catalyst centers among others; environmental sustainability and reduced toxicity being the added benefits. This review briefly deliberates the synthesis pathways for ‘greener’ nanomaterials and their current applications in energy conversion, which may help address the issue of global energy demand. The review aims to endorse the immense potential of bio-based nanostructures in assorted thermal and energy applications, providing a deep insight into further prospects of their appliances that requires deeper understanding and strategic research. The various sectors of energy research where assorted bio-based nanomaterials may find appliances have been discussed. The current challenges and existing limitations in utilizing greener nanomaterials in the energy sector have also been highlighted.
Graphical abstract
... There are two main approaches for the application of down-conversion materials in the perovskite solar cells: one is to introduce the down-conversion materials directly into the functional layers of the perovskite solar cells, and the other one is to deposit an extra layer on the backside of the glass substrates. [124][125][126][127] For examples, Jiang and co-workers [128] used lightemitting materials of Eu 3+ doped TiO 2 , Meng and coworkers [129] doped CeO x into ZnO to successfully construct a down-converting ETL in perovskite solar cells, respectively. It was shown that, when exposed to solar irradiation, the incident visible light can be directly absorbed by the perovskite layer, and part of the high-energy ultraviolet light is converted into low-energy photons by the down-conversion materials and then absorbed by the perovskite layer, thus improving the photogenerated current density and protecting the perovskite layer from UV light damage in the corresponding solar cells, as illustrated in Fig. 13(a). ...
The emerging perovskite solar cells have been recognized as one of the most promising new-generation photovoltaic technologies owing to their potential of high efficiency and low production cost. However, the current perovskite solar cells suffer from some obstacles such as non-radiative charge recombination, mismatched absorption, light induced degradation for the further improvement of the power conversion efficiency and operational stability towards practical application. The rare-earth elements have been recently employed to effectively overcome these drawbacks according to their unique photophysical properties. Herein, the recent progress of the application of rare-earth ions and their functions in perovskite solar cells were systematically reviewed. As it was revealed that the rare-earth ions can be coupled with both charge transport metal oxides and photosensitive perovskites to regulate the thin film formation, and the rare-earth ions are embedded either substitutionally into the crystal lattices to adjust the optoelectronic properties and phase structure, or interstitially at grain boundaries and surface for effective defect passivation. In addition, the reversible oxidation and reduction potential of rare-earth ions can prevent the reduction and oxidation of the targeted materials. Moreover, owing to the presence of numerous energetic transition orbits, the rare-earth elements can convert low-energy infrared photons or high-energy ultraviolet photons into perovskite responsive visible light, to extend spectral response range and avoid high-energy light damage. Therefore, the incorporation of rare-earth elements into the perovskite solar cells have demonstrated promising potentials to simultaneously boost the device efficiency and stability.
