Semi-Analytical Simulation and Optimization of AlGaAs/GaAs <Emphasis Type="Italic">p-i-n</Emphasis> Quantum Well Solar Cell

This paper deals with a AlGaAs/GaAs p-i-n quantum well solar cell. The doped region are based on AlGaAs semiconductor while the intrinsic region “I” contain multi quantum well (MQW) system AlGaAs/GaAs. A semi-analytical model in the intrinsic region and numerical drift-diffusion model in doped regions are combined to extract the total current density of the cell versus voltage. The current-voltage (J-V) characteristics are generated for the AM1.5 solar spectrum. The effect of the Aluminum molar fraction x (Al_xGa_1–xAs), the number, the width, the depth of the wells and barriers in the “i” layer and the doping densities on the electrical outputs of the solar cell are also presented. The optimized solar cell reached a conversion efficiency of 28.72% with a short circuit current density of 36.9 mA/cm² and an open circuit voltage of 0.97 V.     

Design and Optimization of Amorphous Based on Highly Efficient HIT Solar Cell

The objective of this paper is to improve the power conversion efficiency of HIT solar cell using amorphous materials. A high efficiency amorphous material based on two dimensional heterojunction solar cell with thin intrinsic layer is designed and simulated at the research level using Synopsys/RSOFT-Solar Cell utility. The HIT structure composed of TCO/a-Si:H(p)/a-Si:H(i)/c-Si(n)/a-Si:H(i)/a-Si:H(n⁺)/Ag is created by using of RSOFT CAD. Optical characterization of the cell is performed by Diffract MOD model based on RCWA (rigorous coupled wave analysis) algorithm. Electrical characterization of the cell is done by Solar cell utility using based on Ideal diode method. In addition, optimization of the different layer thickness in the HIT structure is executed to improve the absorption and thereby the photocurrent density. The proposed HIT solar cell structure resulted in an open circuit voltage of 0.751 V, a short circuit current density of 36.37 mA/cm² and fill factor of 85.37% contributing to the total power conversion efficiency of 25.91% under AM1.5G. Simulation results showed that the power conversion efficiency is improved by 1.21% as compared to the reference HIT solar cell. This improvement in high efficiency is due to reduction of resistive losses, recombination losses at the hetero junction interface between intrinsic a-Si and c-Si, and optimization of the thicknesses in a-Si and c-Si layers.     

微晶硅电池的制备及提高其效率的优化

采用甚高频等离子体增强化学气相沉积(VHF-PECVD)技术制备了不同硅烷浓度系列的微晶硅电池。结果表明:电池的开路电压随着硅烷浓度的增大而逐渐增加,而电池的短路电流则先增加后减小,在转折点电池的效率达到最大,填充因子则变化不明显;(220)择优取向出现,I(220)/I(111)比值大,电池的短路电流密度也大,电池的效率也最高;在实验的范围内,电池的短路电流密度和厚度成正比例关系;首次在国内制备出了效率达7.3%,短路电流密度(Jsc)为21.7mA/cm2,开路电压(Voc)为0.52V,填充因子(FF)为65%的微晶硅电池。     

CdS量子点敏化TiO2纳米线束阵列太阳能电池的研究

采用水热合成技术,以盐酸、去离子水和酞酸丁酯为反应前驱物,在透明导电玻璃衬底(FTO)上生长TiO2纳米线束阵列,以化学浴沉积技术制备CdS量子点敏化TiO2纳米线束阵列光阳极。研究了CdS量子点敏化的循环周期对太阳能电池的光伏性能、单色光光子-电子转换效率、静态和动态光电流的特性的影响规律。结果表明:CdS量子点的大小和密度随着敏化循环周期的增加而增加,当敏化循环的周期为15次时,单色光光子-电子转换效率最高,电池的短路电流密度为0.61 mA/cm2,开路电压为0.65 V,填充因子为0.50,光电转换效率为0.20%。通过强度调制的光电流谱分析,得到光生电子在光阳极中的扩散系数为3.2×10-6cm2/s,传输时间为2.1×10-2s。     

Gamma irradiated CdS(In)/p-Si heterojunction solar cell

An n-CdS(In)/p-Si heterojunction solar cell was fabricated by vacuum evaporation of a single source of a stoichiometric mixture of CdS and In on a p-Si single crystal wafer at a low temperature of 120°C. The open circuit voltage, short circuit current density, fill factor and conversion efficiency under AM1 were 0.47 V, 20 mA/cm², 0.74 and 7%, respectively. The physical and photoelectric characteristics were measured and discussed. In addition, the cell was irradiated by gamma radiation of 1.25 MeV and its effect on the cell performance was studied. Various preparation parameters such as composition and CdS layer thickness affecting the cell characteristics were investigated before and after exposure to the radiation.     

ZnSe太阳电池

通过掺少量Te提高ZnSe受主杂质浓度，从而制成ZnSe p—n结太阳电池。单结ZnSe光电池在AM1条件下光谱响应半宽度范围365-450nm，波长为400nm时量子效率最大。ZnSe是一种好的叠层多结光电池的顶层材料，可以提供较高的开路电压，并且是底层电池的窗口；在单结ZnSe光电池的基区指数掺杂，95％的区域内能产生大于10^4V／cm的附加电场，在400—475nm波长范围内，该电场可以使其外量子效率增加1～1．5倍。     

A simple analytical treatment of edge-illuminated VMJ silicon solar cells

The series connected silicon vertical multi-junctions (VMJs) solar cells have been suggested as means for ensuring high voltage high efficiency solar cells. This study includes a review of some previously published work concerning the edge-illuminated VMJs solar cells. We introduce a simple one-dimensional analysis to study the high voltage series connected silicon VMJs solar cells. The cell, under study, consists of 40 VMJs. Each junction (unit cell) has dimensions of 250 μm × 0.78 cm × 500 μm. We calculate the short circuit current, the open circuit voltage and the efficiency for an ideal cell, having perfect carrier collection at short circuit conditions, and for real cells. An optimization with respect to the base doping, the emitter doping, the surface recombination velocity and the number of junctions is done for the real cell. A conversion efficiency of 20% has been calculated under AM1.5 light spectrum for real cells having a base doping of 10¹⁶ cm⁻³ and an emitter doping of 10¹⁷ cm⁻³.     

A new route for fabricating CdO/c-Si heterojunction solar cells

CdO/c-Si solar cells have been made by depositing CdO thin films on p-type monocrystalline silicon substrate by means of the rapid thermal oxidation (RTO) technique using a halogen lamp at 350 °C/45 s in static air. Results on structural, optical, and electrical properties of grown CdO films are reported. The electrical and photovoltaic properties of CdO/Si solar cells are examined. Under AM1 illumination condition, the cell shows an open circuit voltage (V_OC) of 500 mV, a short circuit current density (J_SC) of 27.5 mA/cm², a fill factor (FF) of 60%, and a conversion efficiency (η) of 8.84% without using frontal grid contacts and/or post-deposition annealing. Furthermore, the stability of solar cells characteristics is tested.     

Fabrication and characterization of 4-tricyanovinyl-N,N-diethylaniline/p-silicon hybrid organic–inorganic solar cells

Hybrid organic–inorganic solar cell was fabricated by thin film of 4-tricyanovinyl-N,N-diethylaniline deposited on p-Si substrates. The capacitance–voltage characteristics indicated that the junction is of abrupt nature. The dark forward current density-voltage characteristics indicated a tunneling conduction at relatively low voltages followed by a space-charge-limited-conduction mechanism at relatively high voltages. Under illumination, the cell exhibits photovoltaic characteristics with an open-circuit voltage of 0.70 V, a short-circuit current density of 9.15 mA cm⁻², and a power conversion efficiency of 3.10%. The effect of γ-rays irradiation (100 kGy absorbed dose) on the characteristics of the cell was also investigated. The fill factor and the power conversion efficiency decrease by 20.9% and 39% of the original value, respectively.     

High efficiency flexible dye-sensitized solar cells by multiple electrophoretic depositions

A multiple electrophoretic deposition (EPD) of binder-free TiO₂ photoanode has been developed to successfully fill the crack occurring after air-drying on the first EPD-TiO₂ film surface. With the slow 2nd EPD, high quality TiO₂ thin films are acquired on flexible ITO/PEN substrates at room temperature and the device efficiency of the dye-sensitized solar cell achieved 5.54% with a high fill factor of 0.721. Electrochemical impedance spectroscopy measurements analyze the great enhancement of the photovoltaic performance through multiple EPD. The electron diffusion coefficient improved by about 1 order of magnitude in crack-less multiple-EPD TiO₂ films. With the scattering layer, the device reveals a high conversion efficiency of up to 6.63% under AM 1.5 G one sun irradiation, having a short circuit current density, open circuit voltage, and filling factor of 12.06 mA cm⁻², 0.763 V and 0.72, respectively.     

Performance improvement of dual processed perovskite solar cell—acid‐modified ZnO nanorods with Cl‐doped light harvesting layer

Effect of ZnO nanorod surface on fabricating the perovskite solar cell and its performance were studied. Varied thickness of ZnO nanorod arrays with rough surface condition were achieved through the control of hydrothermal growth time and acid treatment. Samples based on modified ZnO nanorod arrays exhibit an impressive increase on the open‐circuit voltage (V_oc) and fill factor (FF) compared with the untreated ones. Further research onto the surface topography and electrochemical impedance spectroscopy test indicates that the improvement should be attributed to the suppression of the charge recombination rate at the ZnO nanorod/CH₃NH₃PbI₃ interface. In order to enhance the short‐circuit current density (J_sc) performance one step further, Cl‐doped perovskite crystal was introduced into the cell. Because of its longer electron diffusion length, an impressive J_sc is received. The final combination of the two methods with the optimized thickness of the ZnO nanorod brought a total power conversion efficiency of 13.3% together with V_oc~0.92 V, J_sc~23.1 mA/cm², and FF~63%. This work highlights the importance of the surface morphology of the electron transport layer and its interface contact with the light absorbing layer in a solar cell structure. Copyright © 2017 John Wiley & Sons, Ltd.     

Theoretical possibilities of InxGa1−xN tandem PV structures

We designed a model of In_xGa_1−xN tandem structure made of N successive p–n junctions going from two junctions for the less sophisticated structure to six junctions for the most sophisticated. We simulated the photocurrent density and the open-circuit voltage of each structure under AM 1.5 illumination in goal to optimize the number of successive junctions forming one structure.For each value of N, we assumed that each junction absorbs the photons that are not absorbed by the preceding one. From the repartition of photons in the solar spectrum and starting from the energy gap of GaN, we fixed the gap of each junction that gives the same amount of photocurrent density in the structure. Then we calculated the current density accurately and optimized the thicknesses of p and n layers of each junction to make it give the same output current density. The evaluation of n_i: the intrinsic concentration permitted to calculate the saturation current density and the open-circuit voltage of each junction. Assuming an overall fill factor of 80%, we divided the output peak power by the incident solar power and obtained the efficiency of each structure.The numerical values for In_xGa_1−xN were taken from the relevant literature. The calculated efficiency goes from 27.49% for the two-junction tandem structure to 40.35% for a six-junction structure. The six-junction In_xGa_1−xN tandem structure has an open-circuit voltage of about 5.34 V and a short circuit current density of 9.1 mA/cm².     

Influence of the layer thickness and hydrogen dilution on electrical properties of large area amorphous silicon p–i–n solar cell

The aim of this work is to present data concerning the optimization of performances of a large area amorphous silicon p–i–n solar cell (30×40 cm²) deposited by plasma enhanced chemical vapour deposition (PECVD) at 27.12 MHz. In this work the solar cell was split into small areas of 0.126 cm², aiming to study the device performance uniformity, where emphasis was put on the role of the n-layer thickness. The solar cells were studied through the spectral response behaviour in the 400–750 nm range as well as by the behaviour of the AC impedance. Solar cells with fill factor of 0.58, open circuit voltage of 0.83 V, short circuit current density of 17.14 mA/cm² and an efficiency of 8% were obtained at growth rates higher than 0.3 nm/s.     

Antireflective coating fabricated by chemical deposition of ZnO for spherical Si solar cells

ZnO thin films as an antireflective (AR) coating have been successfully fabricated on spherical Si solar cells by chemical deposition, which enables uniform film formation. ZnO films were prepared chemically by immersing the cell in an aqueous solution of zinc nitrate and dimethylamineborane maintained at 80 °C. The current–voltage measurements of the solar cells confirmed the increase in short circuit current induced by the AR effect. The open circuit voltage and fill factor were improved by surface passivation. As a result, the conversion efficiency of cells without an AR coating (9.45%) increased to 11.8%, which represents a 25% (relative) increase. The results indicate that the chemical deposition of ZnO is effective for the AR coating of spherical Si solar cells.     

Effect of electron irradiation on the properties of CdTe/CdS solar cells

Polycrystalline CdTe/CdS solar cells are used in space, as well as terrestrial, applications. The results of the studies on the effect of 8 MeV electron irradiation on p-CdTe/n-CdS thin film solar cells prepared by radio frequency (RF) sputtering are presented in this article. Solar cell parameters like short circuit current (I_sc), open circuit voltage (V_oc), fill factor (FF), conversion efficiency (η), saturation current (I_s) and ideality factor (n) have been considered. CdTe thin film solar cells exhibit good stability against electron irradiation up to 100 kGy.     

大面积集成型a－SiC：H／a－Si：H叠层太阳电池的研制

报道了大面积（２７９０ｃｍ２）集成型ａ－ＳｉＣ：Ｈ／ａ－Ｓｉ：Ｈ叠层太阳电池的研制及稳定性实验结果，讨论了限制该电池效率的一些因素。实验电池的性能参数：Ｖｏｃ＝４０．８Ｖ，ＩＳＣ＝５３０．４０ｍＡ，ＦＦ＝４９．４％，有效面积（２２８０ｃｍ２）光电转换效率ＥＦ＝４．６９％（ＡＭ１．５，１００ｍＷｃｍ－２，２５℃）。制备出光电子学性能优良的ａ－ＳｉＣ：Ｈ薄膜及解决电池内部ｎ／Ｐ结的接触问题是提高该电池性能的关键。     

Classification of shunting mechanisms in crystalline silicon solar cells

The efficiency of a solar cell is given by its average electrical parameters. On inhomogeneous materials and especially on large-area solar cells the inhomogeneity of the short circuit current, the open circuit voltage and the fill factor are important factors to reach high and stable efficiencies and may limit the overall performance of the device.A locally increased dark forward current (shunt) reduces the fill factor and the open circuit voltage of the whole cell. The inhomogeneity of the forward current in a solar cell can be measured using lock-in thermography. The quantitative and voltage-dependent evaluation of these thermographic investigations of various solar cell types on mono- or multi-crystalline silicon enables the classification of the different shunting mechanisms found. By further microscopic investigations the physical reasons for the increased dark forward currents can be determined.It turns out that a high density of crystallographic defects like dislocation tangles or microdefects can be responsible for an increased dark forward current. Unexpectedly, grain boundaries in solar cells on multicrystalline silicon do not show any measurable influence on the local dark forward current. In most cases shunts caused by process-induced defects are dominating the current–voltage characteristic at the maximum power point of the solar cell. In commercial solar cells shunts at the edges are most important, followed by shunts beyond the grid lines.     

Investigation of nickel‐63 radioisotope‐powered GaN betavoltaic nuclear battery

This work describes the theoretical and experimental investigation of an in‐house produced ⁶³Ni radioisotope‐powered GaN‐based direct conversion (betavoltaic) nuclear battery. GaN p‐n junction device with 1‐mm² area was fabricated and irradiated by the ⁶³Ni plate source. Short‐circuit current and open‐circuit voltage of the battery were measured, and current‐voltage curves were plotted. The energy stored in battery, maximum power, and efficiency parameters were calculated. Monte Carlo modelling was used to investigate radioisotope's self‐absorption effect, the optimization of semiconductor and source thickness, transport, and penetration of beta particles in semiconductor junction. A large fraction of beta particle energy emitted from ⁶³Ni source is absorbed within 1 μm of the semiconductor junction on the basis of the simulation results. Epitaxial growth of GaN was performed using metal‐organic chemical vapour deposition (MOCVD) system. Monte Carlo simulation with MCNPX was used to determine optimum ⁶³Ni radioactive film thickness. ⁶³Ni film was electroplated on one face of 1‐mm² copper plate and mounted 1 mm over the semiconductor device. A ⁶³Ni source with an apparent activity of 0.31 mCi produced 0.1 ± 0.001 nA short‐circuit current (I_sc), 0.65 V ± 0.0022 open‐circuit voltage (V_oc), and 0.016 nW ± 0.0002 maximum power (P_max) in the semiconductor device. The filling factor (FF) of the betavoltaic cell was 25%, and the conversion efficiency (?) was 0.05%. Finally, experimental results were compared with theoretical calculations.     

TiO2/ZnO/TiO2 sandwich multi‐layer films as a hole‐blocking layer for efficient perovskite solar cells

A continuous and compact hole‐blocking layer is crucial to prevent photocurrent recombination at the photoanode/electrode interface of high‐performance mesostructure perovskite‐based solar cells. Novel TiO₂/ZnO/TiO₂ sandwich multi‐layer compact film prepared as hole‐blocking layer for perovskite solar cell. Herein, TiO₂, ZnO, and TiO₂ layers were successfully deposited by spin‐coating onto FTO glass substrate in sequence. The fill factor and power conversion efficiency of the perovskite solar cell are remarkably improved by the employment of a TiO₂/ZnO/TiO₂ sandwich compact layer. Perovskite solar cell based on TiO₂/ZnO/TiO₂ sandwich film has been observed to exhibit maximum incident‐photon‐to‐current conversion efficiency in the visible region (400–780 nm) and reach a power conversion efficiency of 12.8% under AM1.5G illumination. Copyright © 2016 John Wiley & Sons, Ltd.     

Novel Cu–carbon nanofiber composites for the counter electrodes of dye‐sensitized solar cells

Copper (Cu)‐catalyzed carbon nanofibers (CNFs) were used as an alternative of the conventional platinum‐noble‐metal‐based catalyst at the counter electrode (CE) of a dye‐sensitized solar cell (DSSC). The CNFs were grown on activated carbon microfiber powder (PACF) using chemical vapor deposition (CVD) and the Cu nanoparticles (NPs). The Cu NPs served simultaneous roles: (i) as the CVD catalyst for the growth of the CNFs; (ii) as an enhancer of the electrode conductivity; and (iii) as a catalyst for the reduction reaction. The Cu‐CNF composite was applied as a thin layer on the fluorine‐doped tin oxide glass using the simple doctor blade method. The prepared Cu‐NP‐dispersed PACF/CNF composite was characterized using various spectroscopic techniques, including scanning electron microscopy, Fourier transform infrared ray, X‐ray diffraction, Raman spectroscopy, and transmission electron microscopy. The electrochemical tests showed that the Cu‐PACF/CNFs had a high electrocatalytic activity and low charge transfer resistance (1.26 Ω cm²), using the cyclic voltammetry and electrochemical impedance spectroscopy measurements. The DSSC fabricated with Cu‐PACFs/CNFs exhibited a power conversion efficiency value of 4.36%, open circuit voltage of 0.75 V, short circuit current density of 11.12 mA cm^?2, and fill factor of 54%. The prepared transition metal–CNF composite was simple to develop and can potentially be used as an efficient catalyst at the CE of DSSCs. Copyright © 2014 John Wiley & Sons, Ltd.