Development of highly conducting n-type micro-crystalline silicon oxide thin film and its application in high efficiency amorphous silicon solar cell

Wide band gap and highly conducting n-type nano-crystalline silicon film can have multiple roles in thin film solar cell. We prepared phosphorus doped micro-crystalline silicon oxide films (n-μc-SiO:H) of varying crystalline volume fraction (X_c) and applied some of the selected films in device fabrication, so that it plays the roles of n-layer and back reflector in p-i-n type solar cells. It is generally understood that a higher hydrogen dilution is needed to prepare micro-crystalline silicon, but in case of the n-μc-SiO:H an optimized hydrogen dilution was found suitable for higher X_c. Observed X_c of these films mostly decreased with increased plasma power (for pressure<2.0 Torr), increased gas pressure, flow rate of oxygen source gas and flow rates of PH₃>0.08 sccm. In order to determine deposition conditions for optimized opto-electronic and structural characteristics of the n-μc-SiO:H film, the gas flow rates, plasma power, deposition pressure and substrate temperature were varied. In these films, the X_c, dark conductivity (σ_d) and activation energy (E_a) remained within the range of 0–50%, 3.5×10⁻¹⁰ S/cm to 9.1 S/cm and 0.71 eV to 0.02 eV, respectively. Low power (30 W) and optimized flow rates of H₂ (500 sccm), CO₂ (5 sccm), PH₃ (0.08 sccm) showed the best properties of the n-μc-SiO:H layers and an improved performance of a solar cell. The photovoltaic parameters of one of the cells were as follows, open circuit voltage (V_oc), short circuit current density (J_sc), fill-factor (FF), and photovoltaic conversion efficiency (η) were 950 mV, 15 mA/cm², 64.5% and 9.2% respectively.     

非晶硅太阳电池的衰减与退火

讨论了影响非晶硅太阳电池稳定性的因素,介绍了改善非晶硅材料稳定性的方法,进行了非晶硅太阳电池光致衰减测试.描述了电流注入退火和热退火对非晶硅太阳电池性能的改善.     

多晶硅太阳电池的氮化硅钝化

全面介绍了等离子增强化学汽相沉积 ( PECVD)纳米氮化硅 ( Si Nx∶ H)光电薄膜的技术发展及现状 ,分析了 PECVD法沉积的 Si Nx∶ H薄膜对多晶硅太阳电池的体钝化和表面钝化机理     

N 型背接触晶硅太阳电池前表面场研究

利用 Silvaco 公司的 Athena 工艺仿真软件和 Atlas 器件仿真软件,对 N 型插指背结背接触(InterdigitatedBack Contact,IBC)晶硅太阳电池普遍采用的前表面场（FSF）结构进行研究,详细分析了 IBC 晶硅电池 FSF 表面掺杂浓度及扩散深度对电池性能的影响。结果表明：具有不同表面掺杂浓度和扩散深度的 FSF 对 IBC 晶硅太阳电池短路电流密度(Jsc)、开路电压(Voc)和填充因子(FF)产生显著影响,从而影响电池的转换效率(Eff)。具有较低表面浓度、深扩散 FSF 结构的 IBC 晶硅太阳电池可获得较高转换效率,当表面掺杂浓度为 5×1017cm–3时,电池转换效率Eff最高,且随 FSF 扩散深度增加略有增加,最高转换效率可达 22.3%。     

Electron‐beam crystallized large grained silicon solar cell on glass substrate

Thin film hetero‐emitter solar cells with large‐grained poly‐silicon absorbers of around 10 µm thickness have been prepared on glass. The basis of the cell concept is electron‐beam‐crystallization of an amorphous or nanocrystalline silicon layer deposited onto a SiC:B layer. The SiC:B layer covers a commercially well available glass substrate, serving as diffusion barrier, contact layer and dopand source. For silicon absorber deposition a low pressure chemical vapour deposition was used. The successively applied e‐beam crystallization process creates poly‐silicon layers with grain sizes up to 1 × 10 mm² with low defect densities. The high electronic quality of the absorber is reflected in open circuit voltages as high as 545 mV, which are realized making use of the well‐developed a‐Si:H hetero‐emitter technology. Copyright © 2011 John Wiley & Sons, Ltd.     

空间太阳电池硅单晶的辐射效应及加固

概述了硅太阳电池和硅单晶在空间高能粒子辐射下性能的变化及采用掺锡、掺锂提高太阳电池用硅单晶抗辐射性能的原理和方法。     

Two‐dimensional modeling of front contact silicon solar cells

The modeling of a new type of silicon solar cell intended for operation at very high concentration, with all the contacts at its front face, is presented. The two‐dimensional model developed makes use of the theory of the complex variable, and is able to explain the main features of the operation of these cells. It is shown that if all the parameters reach good state‐of‐the‐art values, and with the appropriate layout, this structure can reach 25% efficiency for a range of concentrations wider than any other known silicon cell. Copyright © 2004 John Wiley & Sons, Ltd.     

Epitaxial solar cells on titanium-doped silicon substrates

Single crystal substrates (0.2 Ω cm, boron doped) purposely doped at 2 × 10¹⁴ cm⁻³ with titanium were used to assess the effect of titanium on solar cell performance. Comparisons were made of all-epitaxial, diffused junction epitaxial, and all diffused junction solar cells fabricated on these substrates. In all cases lower than normal short-circuit current densities were obtained due to diminished red response. However, the short-circuit currents and efficiencies for the epitaxial cells were higher than those for the cells made by direct diffusion into the bulk titanium-doped silicon. The highest efficiency obtained for an epitaxial cell on a titanium-doped substrate was 11.7%. The research reported herein was supported by Jet Propulsion Laboratory, California Institute of Technology under contract No. 954817 and RCA Laboratories, David Sarnoff Research Center, Princeton, New Jersey.     

Properties of Rapidly-Grown rtr silicon sheet and their effects on solar cell processing

Silicon sheet grown by the Ribbon-to-Ribbon (RTR) crystal growth method exhibits characteristics that are unusual relative to solar cell processing on conventional silicon wafers. One such characteristic is the low (5-15 ym) minority carrier diffusion length observed in as-grown ribbons. This value is increased to as high as 100 ym due to a two step getter ing effect that results from the normal process sequence used for solar cell fabrication. A second characteristic reported here is a dense macroscopic dendritic structure which occurs at the higher growth rates. This presents a very irregular, non-planar surface onto which solar cells can be fabricated. The characteristics of solar cells made on dendritic ribbon are similar to those made on ribbons that do not contain dendrites.     

Interdigitated back‐contact heterojunction solar cell concept for liquid phase crystallized thin‐film silicon on glass

We present an interdigitated back‐contact silicon heterojunction system designed for liquid‐phase crystallized thin‐film (~10 µm) silicon on glass. The preparation of the interdigitated emitter (a‐Si:H(p)) and absorber (a‐Si:H(n)) contact layers relies on the etch selectivity of doped amorphous silicon layers in alkaline solutions. The etch rates of a‐Si:H(n) and a‐Si:H(p) in 0.6% NaOH were determined and interdigitated back‐contact silicon heterojunction solar cells with two different metallizations, namely Al and ITO/Ag electrodes, were evaluated regarding electrical and optical properties. An additional random pyramid texture on the back side provides short‐circuit current density (j_SC) of up to 30.3 mA/cm² using the ITO/Ag metallization. The maximum efficiency of 10.5% is mainly limited by a low of fill factor of 57%. However, the high j_SC, as well as V_OC values of 633 mV and pseudo‐fill factors of 77%, underline the high potential of this approach. Copyright © 2015 John Wiley & Sons, Ltd.     

Design of Ag nanograting for broadband absorption enhancement in amorphous silicon thin film solar cells

Light trapping is one of the key issues to improve the light absorption and increase the efficiency of thin film solar cells. The effects of the triangular Ag nanograting on the absorption of amorphous silicon solar cells were investigated by a numerical simulation based on the finite element method. The light absorption under different angle and area of the grating has been calculated. Furthermore, the light absorption with different incident angle has been calculated. The optimization results show that the absorption of the solar cell with triangular Ag nanograting structure and anti-reflection film is enhanced up to 96% under AM1.5 illumination in the 300–800 nm wavelength range compared with the reference cell. The physical mechanisms of absorption enhancement in different wavelength range have been discussed. Furthermore, the solar cell with the Ag nanograting is much less sensitive to the angle of incident light. These results are promising for the design of amorphous silicon thin film solar cells with enhanced performance.     

Silicon coating of ceramic substrates for low cost solar cell applications

Mullite ceramic substrates were coated with silicon using a unique method of growth designed to produce low-cost material suitable for terrestial based solar cell applications. Pieces of mullite were carbon coated on one side and then dipped into molten silicon. The silicon wet the mullite only where the carbon was applied. Directional solidification occurs upon withdrawal. The film thicknesses were reasonably uniform over the area and could be controlled by varying the melt temperature and withdrawal rate, with higher temperatures and faster pull rates giving thinner films. Typical thicknesses of dip coated layers ranged between 20 and 150ym. The layers consist of large elongated grains aligned in the direction of withdrawal. The mullite substrates are slowly dissolved by the molten silicon resulting in some contamination of the silicon layers upon solidification. Glassy carboncoatings were found to be essentially impervious to the molten silicon and prevented dissolution of the substrate even after one hour of immersion. Cells of 1 cm² active area having J_SC This paper presents results of research performed for the Low-Cost Solar Array Project, Jet Propulsion Laboratory, California Institute of Technology, sponsored by the Department of Energy through an interagency agreement with the National Aeronautics and Space Administration. as high as 26.8 mA/cm² at 100 mW/cm² illumination with efficiencies of 9.6% were made from these layers. Solar cell properties have shown steady improvement as growth conditions and cell fabrication procedures have improved, so that siliconon-ceramic appears quite promising as a cost-effective solar cell material.     

Characterization of laser carved micro channel polycrystalline silicon solar cell

In this study the efficiency of polycrystalline silicon solar cells was increased carving micro channel structures using a laser. In research to date, micro channel structures on the surface of polycrystalline silicon solar cells have been manufactured and studied. In an experiment polycrystalline silicon solar cell with micro channel structures on the surface demonstrated an increase in efficiency of 0.23-1.50%, as the radius of the micro channel structures varied from 15 μm to 35 μm. Micro channels also improved the Fill Factor of polycrystalline silicon solar cells. However, the efficiency started to decrease when the radius of the micro channel structures was greater than 40 μm. Detailed features of the variation in current voltage of polycrystalline silicon solar cells with micro channels are discussed.     

非、单晶硅太阳能电池组件比功率发电量对比研究

通过比较单晶硅与非晶硅比功率发电量,分析两者在太阳能发电功效上的具体差异.     

A simple analytical model of thin films crystalline silicon solar cell with quasi-monocrystalline porous silicon at the backside

An analytical model that simulates the performance of an elementary thin silicon solar cell with a thin film quasi-monocrystalline porous silicon (QMPS) at the backside reflector is developed. A complete set of equations for the photocurrent generated under the effect of the reflected light is solved analytically in each region. The collection of the light absorbed by the QMPS layer has been discussed and the analytical solution of the light-generated current in this layer is derived. The maximum of the photocurrent density calculated in the present study is in accordance with the numerical values established by Bergmann et al. Furthermore, the influence that the layer's number of double porosities and high porosity have on the photovoltaic parameters is studied. It is demonstrated that the photovoltaic parameters increase with the number of double porosities that the layer might have in a given structure. When the QMPS layer is formed by three double-porosity layers 20%/80% and for a 5-μm-thick film c-Si, the backside reflector gives a total improvement of about 6 mA/cm² for the photocurrent density and 3.2% for the cell efficiency.     

Performance of front contact silicon solar cells under concentration

The first realization of a new type of silicon solar cell intended for operation at very high concentration, with all the contacts at its front face, is presented. Although the efficiencies achieved are not outstanding, the feasibility of the structure is proven by the fabrication of several thousands of cells with similar performance. Modeling has evidenced the main routes for improvement. Efficiencies close to 25% for a range of efficiencies from 80 to 560 suns are predicted as achievable for cells with state‐of‐the‐art technology and appropriate layout. Copyright © 2004 John Wiley & Sons, Ltd.     

Capacitance transient spectra of processing- and radiation-induced defects in silicon solar cells

Capacitance transient spectroscopy is used to study defects in chips of fully fabricated silicon solar cells. Characteristic differences are observed as a function of the crystal growth type (crucible grown or float zoned) and dopant (boron or aluminum) of the starting material, processing variables (diffused or implanted junctions, electron beam or furnace annealing) and radiation environment (1 MeV electron irradiation).     

Gettering by heat thermal processing: application in crystalline silicon solar cells

The aim of this work is to getter unwanted impurities from solar grade crystalline silicon (Si) wafers and then to enhance their electronic properties. This was done by forming a sacrificial porous silicon (PS) layer on both sides of the Si wafers and by performing infrared (IR) thermal annealing treatments (at around 950 °C) in a SiCl₄/N₂ controlled atmosphere. The process allows concentrating unwanted impurities in the PS layer and near the PS/silicon interface. These treatments reduce the resistivity by about two orders of magnitude at a depth of about 40 μm and improve the minority carrier diffusion length from 75 to 210 μm. This gettering method was also tested on silicon wafers where grooved fingers and back contacts were achieved using a chemical vapor etching (CVE) method. Front buried metallic contacts and small holes for local back surface field were then achieved after the gettering stage in order to realize silicon solar cells. It was shown that the photovoltaic parameters of gettered silicon solar cells were improved as regard to ungettered ones.     

扩散温度和时间对晶体硅太阳电池性能的影响

研究了薄层方块电阻对单晶硅太阳电池的开路电压(Voc)、短路电流(Isc)、填充因子(FF)和转换效率(η)的影响.通过控制扩散温度和时间制备了具有不同薄层方块电阻的单晶硅太阳电池.结果表明:当扩散温度和时间分别为863℃和1 050 s时,电池性能得到了有效的改善,其平均开路电压、短路电流、填充因子和转换效率分别为0.64V,5.58A,0.755和17.3％.     

超薄PCBM层提高有机太阳电池效率

为研究超薄PCBM层对有机太阳电池的影响,制备了含和不含超薄PCBM层的两种不同结构的体相异质结太阳电池,电池结构分别为:ITO/PEDOT:PSS/P3HT+PCBM/PCBM/AI,ITO/PEDOT:PSS/P3HT+PCBM/Al.测试结果表明:所制备电池的开路电压分别为0.599 2V和0.572 7 V,能量转换效率分别为2.24％、1.21％,超薄PCBM层起到了电子传输的作用.