Analysis of the fill factor for n-CdS/p-CdTe solar cells

The fill factor is calculated for a solar cell with series and parallel resistance, and with a voltage-dependent collection function for the light current that is important for solar cells using high optical absorption coefficient materials, or with significant junction interface recombination velocities. A parametric approach is used that is helpful and physically clarifying. Good agreement is demonstrated between the theoretical prediction and the experimental results for an 8% efficient n-CdS/p-CdTe heterojunction solar cell produced in our laboratory.     

Low resistance ohmic contacts to n- and p-InP

The contact properties of various metal combinations, deposited by vacuum evaporation on InP, were studied. Among these metal combinations, Au/Ge + Ni and Au/Zn proved to be most suitable. The former on n-InP (n = 8 × 10¹⁷/cm³) and the latter on p-InP (p = 9 × 10¹⁷/cm³) exhibited specific contact resistances as low as 1.2 × 10^?6 and 1.1 × 10^?4 Ωcm², respectively. The specific contact resistances were analyzed using a four-point method which also accounts for the spreading resistance. Furthermore, the resistances of metal contacts to InP were calculated as a function of doping concentration and were compared with the experimental results. The described contacting technique was successfully applied to the preparation of quaternary lasers.     

Junction potentials of strongly illuminated n+ - p - p+ solar cells

The low-junction (LHJ) model is applied to an n⁺ - p - p⁺ solar cell having finite dimensions, in order to investigate its performance under intense illumination. Ambipolar transport equations are solved in the three sections of the cell using appropriate boundary conditions. Expressions for junction currents are derived, and the junction potentials under open-circuit conditions are computed by the Newton-Raphson method.The theory presented here includes the effects of high level injection. The generalized current density equations which are derived here for an n⁺ - p - p⁺ device are shown to reduce to the ideal Shockley diode equation with appropriate modifications. The effects of p - p⁺ low-high junction on the open-circuit voltage of the cell are explained. The theoretical results of this paper are consistent with the experimental results of others.     

High conversion efficiency p-n+InP homojunction solar cells

p-n⁺InP homojunction solar cells have been fabricated and investigated. The best experimental cell without an antireflection coating exhibits a conversion efficiency of 13.5 percent (active area) under AM1 illumination; the corresponding open-circuit voltage, short-circuit current density, and fill factor (F.F.) are 0.817 V, 21.0 mA/cm², and 0.787, respectively.     

Ultrahigh (100%) barrier modification of n-InP Schottky diode by DNA biopolymer nanofilms

Here I demonstrate that DNA biopolymer molecules can control the electrical characteristics of conventional Al/n-InP metal-semiconductor contacts. Results show that DNA increases an effective barrier height as high as 0.87 eV by influencing the space charge region of n-InP device with a good rectifying behavior.     

High injection phenomena in p+in+ silicon solar cells

A very simple analytic analysis of p⁺in⁺ solar cell structures is undertaken based in the quasi-neutrality condition (n = p), which validity is verified. The only differential equation to be solved in the model is the classical continuity one. Non linearities, appea ronly in the boundary conditions. This model can be applied to p⁺nn⁺ or n⁺pp⁺ cells under very high injection conditions. High carrier concentrations are required to support the current flow even in short-circuit conditions, so enhancing the recombination which, on the other hand, is reduced by high injection lifetime increase. Under-linearity between the short-circuit current and the photon flux is also deduced at very high irradiance. The short-circuit current under bifacial illumination is higher than the sum of those currents under front and back illumination alternatively, so leading to inherently better bifacial cells. In the V_oc vs J_sc curve values of m in the logarithmic slope mkT/q range from values slightly below one to two. The value m = 1 is not to be expected even if the base recombination is negligible due to Dember potential effects.     

近空间升华法制备高取向硒化锑薄膜太阳电池

硒化锑太阳电池以其原材料丰富、工艺简单和结 构稳定等优势,近年来得到了快速发 展。本论文采用近空间升华法制备硒化锑光电薄膜,并对硒化锑的生长进行了机理研究和参 数优化。结果显示:衬底温度的提升有助于硒化锑薄膜的晶化。当衬底温度为 340 ℃时,薄 膜具有较高的晶化率和致密的表面形貌。另一方面,蒸发间距的改变能够调制硒化锑薄膜的 择优取向。当蒸发间距为10 mm时,薄膜具有明显的(002)取向的择优,对应(Sb₄Se₆)n带 垂直于衬底生长,使硒化锑光吸收层具有优异的载流子传输特性。将优化好的硒化锑薄膜应 用到太阳电池中,以FTO/CdS/Sb₂Se₃/P3HT/C的器件结构,获得了5.78%的光电转换效率,其 中开路电压为0.375 V,短路电流密度为28.01 mA/cm²,填充因子为54.94%。以上研究为高 取向性硒化锑太阳电池的优化制备提供了技术路线,并显示出了硒化锑太阳电池的研究潜力 。     

High‐efficiency GaInP/GaAs/GaInNAs solar cells grown by combined MBE‐MOCVD technique

Triple‐junction GaInP/GaAs/GaInNAs solar cells with conversion efficiency of ~29% at AM0 are demonstrated using a combination of molecular beam epitaxy (MBE) and metal‐organic chemical vapor deposition (MOCVD) processes. The bottom junction made of GaInNAs was first grown on a GaAs substrate by MBE and then transferred to an MOCVD system for subsequent overgrowth of the two top junctions. The process produced repeatable cell characteristics and uniform efficiency pattern over 4‐inch wafers. Combining the advantages offered by MBE and MOCVD opens a new perspective for fabrication of high‐efficiency tandem solar cells with three or more junctions. Copyright © 2016 John Wiley & Sons, Ltd.     

High efficiency polycrystalline silicon solar cells by continuous plasma deposition and laser recrystallization

Solar cells of up to 12% efficiency have been fabricated on laser recrystallized fine grain polycrystalline silicon films produced by high pressure plasma (hpp) aided hydrogen reduction of trichlorosilane. The hpp system was operated in a continual mode to produce microcrystalline silicon films continually using finite size temporary molybdenum substrates. The major improvement over previous devices of this type is in the elimination of oxygen contamination during laser recrystallization. This resulted in a reduction in the dark excess junction current and improvement in minority carrier diffusion length. The devices are found to be diffusion limited, with diffusion current coefficients in the range of 3 × 10^-12to 5 × 10^-12A/cm²when the base resistivity was 0.4 to 0.5 Ω-cm p-type.     

High efficiency inversion layer solar cells on polycrystalline silicon by the application of silicon nitride

Plasma enhanced CVD silicon nitride is introduced for the fabrication of inversion layer solar cells on p-type polycrystalline silicon. The same high interface quality as obtained for Si-nitride on monocrystalline silicon could also be achieved for polycrystalline silicon. This includes high interface charge densities up to 6.6 × 10¹²cm^-2and high UV sensitivity of the cells. For 4-cm²polycrystalline metal-insulator-semiconductor inversion layer (MIS/IL) solar cells active area efficiencies up to 13.4 percent (12.3-percent total area efficiency) under AM1 illumination could be reached, the highest values yet reported for polycrystalline silicon inversion layer solar cells on a total area basis. For the coprocessed MIS/IL cells on monocrystalline 0.7-ω. cm p-Si     

High efficiency polycrystalline silicon solar cells using lowtemperature PECVD process

Conventionally directionally solidified (DS) and silicon film (SF) polycrystalline silicon solar cells are fabricated using gettering and low temperature plasma enhanced chemical vapor deposition (PECVD) passivation. Thin layer (~10 nm) of PECVD SiO₂ is used to passivate the emitter of the solar cell, while direct hydrogen rf plasma and PECVD silicon nitride (Si₃N₄) are implemented to provide emitter and bulk passivation. It is found in this work that hydrogen rf plasma can significantly improve the solar cell blue and long wavelength responses when it is performed through a thin layer of PECVD Si₃N₄. High efficiency DS and SF polycrystalline silicon solar cells have been achieved using a simple solar cell process with uniform emitter, Al/POCl₃ gettering, hydrogen rf plasma/PECVD Si₃N₄ and PECVD SiO₂ passivation. On the other hand, a comprehensive experimental study of the characteristics of the PECVD Si₃N₄ layer and its role in improving the efficiency of polycrystalline silicon solar cells is carried out in this paper. For the polycrystalline silicon used in this investigation, it is found that the PECVD Si₃N₄ layer doesn't provide a sufficient cap for the out diffusion of hydrogen at temperatures higher than 500°C. Low temperature (⩽400°C) annealing of the PECVD Si₃N ₄ provides efficient hydrogen bulk passivation, while higher temperature annealing relaxes the deposition induced stress and improves mainly the short wavelength (blue) response of the solar cells     

基于LM3481的太阳能板DC/DC高效变换器

TI生产的LM3481将开关电源的输入电压范围降低到了一个新台阶,最低工作电压仅2.9V.分析和研究采用PWM方法调制的高性能稳压控制芯片LM3481,以其为核心设计制作了一款体积小、功耗低、频率高、输入范围宽的DC/DC升降压型变换器,电路采用SEPIC拓扑结构.实测表明：LM3481 DC/DC变换器特别适合于物联网中的小型太阳能供电系统对3.3V电压的需求,能够很好地将不稳定的太阳能板输出电压转换为稳定电压供负载节点长久使用.LM3481给出了一个比单靠电池供电更优化的电源解决方案.     

Carrier temperature effects in a p−n junction

Carrier temperature effects arising in a p?n junction are discussed by solving a chosen set of conservation equations. An analytic solution is found for the current flow assuming small departures of the carrier temperature from equilibrium, and a numerical solution involving large carrier temperature variations is presented. The reverse bias at which avalanche breakdown is predicted for a germanium diode is in agreement with experiment.     

Temperature coefficient of resistance for p- and n-type silicon

The temperature coefficient of resistance for n- and p-type silicon has been calculated between ?50 and 125°C for a wide range of concentrations and levels of compensation. These results provide a useful guide for the design of silicon integrated resistors.     

High efficiency screen printed bifacial solar cells on monocrystalline CZ silicon

We present industrialized bifacial solar cells on large area (149 cm²) 2 cm CZ monocrystalline silicon wafers processed with industrially relevant techniques such as liquid source BBr₃ and POCl₃ open‐tube furnace diffusions, plasma enhanced chemical vapor deposition (PECVD) SiN_x deposition, and screen printed contacts. The fundamental analysis of the paste using at boron‐diffused surface and the bifacial solar cell firing cycle has been investigated. The resulting solar cells have front and rear efficiencies of 16.6 and 12.8%, respectively. The ratio of the rear J_SC to front J_SC is 76.8%. It increases the bifacial power by 15.4% over a conventional solar cell at 20% of 1‐sun rear illumination, which equals to the power of a conventional solar cell with 19.2% efficiency. We also present a bifacial glass–glass photovoltaic (PV) module with 30 bifacial cells with the electrical characteristics. Copyright © 2010 John Wiley & Sons, Ltd.     

Thin film polycrystalline Si p-n junction solar cells with preferential doping

A model has been introduced for a polycrystalline thin film silicon p-n junction solar cell with preferential doping along the grain boundaries. Detailed numerical calculations have been done for the effect of doping depths along the grain boundaries, for different grain sizes, on the performance of the cell under AM1 conditions. The results indicate that preferential doping of grain boundaries leads to significant improvement of the cell performance.     

High efficiency polymer solar cells with wet deposited plasmonic gold nanodots

We report the enhanced performance of poly(3-hexylthiophene)/[6,6]-phenyl-C₆₁ butyric acid methyl ester (P3HT/PCBM) bulk heterojunction solar cells with wet deposited interfacial gold nanostructures on their indium tin oxide (ITO) surfaces. To produce localized surface plasmons at the ITO surfaces, gold nanostructures were fabricated through the layer-by-layer deposition of gold nanorods onto the ITO substrates and transformed into nanodots through a thermally induced shape transition. The incorporation of plasmonic gold nanodots on the ITO surface was found to result in an increase in the power conversion efficiency from 3.04% to 3.65%, which is due to the presence of the resulting plasmon field.     

High efficiency arrays of polymer solar cells fabricated by spray‐coating in air

We present bulk heterojunction organic solar cells fabricated by spray‐casting both the PEDOT:PSS hole‐transport layer (HTL) and active PBDTTT‐EFT:PC₇₁BM layers in air. Devices were fabricated in a (6 × 6) array across a large‐area substrate (25 cm²) with each pixel having an active area of 6.45 mm². We show that the film uniformity and operational homogeneity of the devices are excellent. The champion device with spray cast active layer on spin cast PEDOT:PSS had an power conversion efficiency (PCE) of 8.75%, and the best device with spray cast active layer and PEDOT:PSS had a PCE of 8.06%. The impacts of air and light exposure of the active layer on device performance are investigated and found to be detrimental. Copyright © 2015 John Wiley & Sons, Ltd.     

Some properties of ion-implanted p−n junctions in silicon

Diodes have been made by implantation of boron or gallium ions in n-type, and phosphorus ions in p-type silicon. The doses range from 5 × 10¹² to 10¹⁵ ions/cm², and the energies from 20 to 70 keV. In all diodes the reverse current shows a sharp recovery step upon annealing at 500–600°C. The reverse current after this annealing is typically of the order of 1 nA/cm² at 1 V reverse bias. To overcome the problem of low breakdown voltages usually found for implanted junctions, methods have been developed to enlarge the effective radius of curvature at the edge of the implanted junction. In a planar process with oxide masking, breakdown voltages of 150 V for 3 Ωcm or 1500 V for 300 Ωcm silicon are obtained. This is done by implanting the ions through a tapered oxide, where the oxide walls make an angle of only 3–5° with the silicon surface. The junction depth in this case is 0.4 μm.Another method uses a mask, placed free in front of the slice. Slice and mask rotate during implantation. In this way, a breakdown voltage of 2700 V is obtained with 300 Ωcm silicon.