硅太阳能电池光谱响应曲线测定研究性实验

采用溴钨灯作为光源,运用光栅单色仪选择不同频率的光照射硅太阳能电池,测得了不同波长光照时的短路电流,通过与入射光强和光子能量相除,获得了硅太阳能电池的相对光谱响应曲线,实验曲线与理论曲线符合得较好.     

对硅薄膜型太阳电池的一些思考

在当前迅速发展的绿色环保能源中,硅太阳电池一直占据着首要地位.然而晶体硅太阳电池(单晶硅和多晶硅)由于价格昂贵和材料短缺已不能满足绿色能源快速发展的需要.因此,薄膜型太阳电池已经被视为今后发展的主要方向.非晶硅薄膜太阳电池虽然在性能上还具有不少缺点,但随着薄膜沉积技术的改进以及膜本身质量的不断提高,它在太阳电池领域中仍占有一席之地.多晶硅薄膜太阳电池集晶体硅与非晶硅电池的优点为一体,也受到人们的关注.然而,后起之秀纳米硅薄膜太阳电池,依靠其本身的优越性以及当前纳米技术的进展,将会成为一个新的亮点.     

Advanced solar materials for thin-film photovoltaic cells

As one of the most promising solutions for the green energy, thin-film photovoltaic cell technology is still immature and far from large-scale industrialization. The major issue is getting low cost and stable module efficiency. To solve these problems, a large amount of advanced solar materials have been developed to improve all parts of solar cell modules. Here, some new solar material developments applied in different critical parts of chalcogenide thin-film photovoltaic cells are reviewed. The main efforts are focused on improving light trapping and antireflection, internal quantum efficiency and collection of photo-generated carriers.     

锥形二维光子晶体太阳电池数值模拟

采用时域有限差分方法,模拟研究在本征吸收层引入锥形二维光子晶体(2D PC)后,其结构参数变化对单结微晶硅电池各膜层吸收的影响规律.研究表明,2D PC的纵横比(高度与周期之比)对电池本征吸收具有决定性影响.周期小于1μm时,本征吸收随着纵横比的增大先上升后下降,纵横比为1时达到最大值;周期大于1μm时,本征吸收达到最大值的纵横比小于1,且周期越大,实现本征吸收最大化的纵横比越小.当周期为0.5μm,纵横比为1时,锥形2D PC电池的本征吸收达到峰值,短路电流密度为27.8 mA/cm2;与平面结构相比,短路电流密度提升5.8 mA/cm~2,相对增加27%.该研究突破了以往认为绒面陷光效果主要取决于绒面形貌横向特征尺寸的观点,对实验获取最佳的周期或随机绒面陷光结构具有指导意义.     

Investigation on antireflection coatings for Al:ZnO in silicon thin-film solar cells

We numerically investigate the role of antireflection (AR) coatings, composed of SiO₂ and/or ZnO, in suppression of interfacial reflections in the presence of the transparent conducting oxide, Al-doped ZnO (AZO). Three structures are simulated: (a) AR coatings in organic light-emitting diodes (OLEDs) and flat panel displays, (b) AR coating located between the glass and the AZO, and (c) same as the case b except the involvement of another AR coating between the AZO and the amorphous silicon layers. The weighted average transmittance according to the AM1.5 solar spectrum, the photovoltaic transmittance (T_pv), suggests that there is no evident difference between the structures a and b, especially when the layer number of AR coatings is less than three. An effective way to improve T_pv is presented in the structure c, where T_pv is increased from 73.54% to 76.32% with a three-layered AR coating located between AZO and a-Si. It implies that the suppression of interfacial reflections, resulting from the considerable mismatch of refractive indices at the interface of AZO and a-Si, would benefit the efficiency improvement of silicon thin-film solar cells.     

Design of periodic metal-insulator-metal waveguide back structures for the enhancement of light absorption in thin-film solar cells

To increase the absorption in a thin layer of absorbing material (amorphous silicon, a-Si), a light trapping design is presented. The designed structure incorporates periodic metal-insulator-metal waveguides to enhance the optical path length of light within the solar cells. The new design can result in broadband optical absorption enhancement not only for transverse magnetic (TM)-polarized light, but also for transverse electric (TE)-polarized light. No plasmonic modes can be excited in TE-polarization, but because of the coupling into the a-Si planar waveguide guiding modes and the diffraction of light by the bottom periodic structures into higher diffraction orders, the total absorption in the active region is also increased. The results from rigorous coupled wave analysis show that the overall optical absorption in the active layer can be greatly enhanced by up to 40%. The designed structures presented in this paper can be integrated with back contact technology to potentially produce high-efficiency thin-film solar cell devices.     

High critical oxygen concentration in microcrystalline silicon solar cells

For microcrystalline silicon based p–i–n solar cells the effect of deposition conditions on the critical oxygen concentration was investigated. All solar cells were prepared by 13.56 MHz plasma‐enhanced chemical vapour deposition. The critical oxygen concentration defines the lowest oxygen concentration in the intrinsic absorber layer causing a deterioration of the solar cell performance. For intentional contamination of ～1.2–1.3 µm thick i‐layers, the oxygen was inserted by a controllable leak at the process gases supply line, i.e. by a gas pipe leak. For µc‐Si:H deposited at a discharge power of 0.53 W/cm² we find a critical oxygen concentration of 1–2 × 10¹⁹ cm^–3 in agreement with values commonly reported in literature. However, changing the deposition conditions, we find that the critical oxygen concentration in µc‐Si:H cells is not fixed. At reduced power of 0.20 W/cm² a much higher value for the critical oxygen concentration of 1 × 10²⁰ cm^–3 is observed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Heavily doped Si:P emitters of crystalline Si solar cells: recombination due to phosphorus precipitation

The measured saturation current density J_0e of heavily phosphorus‐doped emitters of crystalline Si solar cells is analysed by means of sophisticated numerical device modelling. It is concluded that Shockley–Read–Hall (SRH) recombination exceeds Auger recombination significantly; it is caused by inactive phosphorus. This explains the large discrepancies between measured and simulated J_0e values, observed persist‐ently over the last two decades in industrially fabricated Si solar cells. As a consequence, the heavily phosphorus‐diffused emitters still bear a significant potential to contribute to higher Si solar cell efficiency levels, if the amount of inactive phosphorus can be reduced. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

钙钛矿薄膜气相制备的晶粒尺寸优化及高效光伏转换

钙钛矿薄膜的气相制备是一种极具潜力的工业化生产工艺,但薄膜的质量控制目前远落后于溶液制备法.本文通过建立PbI_2薄膜向钙钛矿薄膜完全转化过程中反应时间、晶粒尺寸与温度的关系,实现了薄膜的质量优化及大面积钙钛矿薄膜的制备,将薄膜的平均晶粒粒径从0.42μm优化到0.81μm.基于空间电荷限制电流模型对缺陷密度的研究显示,钙钛矿薄膜的缺陷密度由5.90×10~(16)cm~(–3)降低到2.66×10~(16)cm~(–3).光伏器件(FTO/TiO_2/C_(60)/MAPbI_3/spiro-OMeTAD/Au结构)测试显示,面积为0.045cm~2器件的平均光电转换效率从14.00%提升到17.42%,最佳光电转换效率达到17.80%,迟滞因子减小至4.04%.同时,基于180℃制备的1cm~2器件的光电转换效率达到13.17%.     

步进扫描时间分辨光谱及其在太阳电池光电导上的应用

建立傅里叶变换步进扫描时间分辨光电导光谱，并研究太阳电池中与转换效率密切相关的少数载流子寿命.实验选取三种典型的硅太阳电池(单晶硅样品1、多晶硅样品2和多晶硅样品3 )，发现其瞬态光电导的上升和衰退曲线可以分别用两个简单的指数函数描述.由于有复合中心的参与，复合过程中少数载流子的寿命比产生过程中的寿命短.为验证实验结果的可靠性，采用了提取样品少数载流子的体寿命和计算其有效扩散长度两种方法.通过与太阳电池暗伏安特性和负载特性研究相结合，进一步分析和讨论了少数载流子寿命与短路电流、开路电压和转换效率的关系.同时探讨了步进扫描时间分辨光谱实验的其他用途. 关键词： 步进扫描 时间分辨 硅太阳电池 瞬态光电导     

甚高频等离子体增强化学气相沉积制备微晶硅太阳电池的研究

采用甚高频等离子体增强化学气相沉积技术成功地制备了不同硅烷浓度和辉光功率条件下的微晶硅电池.电池的J-V测试结果表明：在实验的硅烷浓度和功率范围内，随硅烷浓度的降低和功率的加大，对应电池的开路电压逐渐变小；硅烷浓度的不同对电池的短路电流密 度有很大的影响，但功率的影响在实验研究的范围内不是很显著.对于微晶硅电池，N层最好 是非晶硅，这是因为一方面可以降低对电流的横向收集效应，另一方面也降低了电池的漏电概率，提高了电池的填充因子. 关键词： 微晶硅太阳电池 甚高频等离子体增强化学气相沉积     

Nanosilver surface plasmon response enhanced the photovoltaic performance of organic solar cells

Nanosilver island thin films with different thickness were synthesized by vacuum vapor deposition between ITO and PEDOT:PSS for organic solar cells, forming the structure of ITO/AgNPs layer/PEDOT:PSS/P3HT:PCBM/LiF/Al. Surface morphology and UV–vis absorption spectrum were investigated by AFM and UV–vis scanning spectrophotometer. It was found that after adding the nanosilver film, the optical properties of the device were enhanced with increasing the thickness of nanosilver island films. When the thickness of nanosilver thin films is 3.0 nm, the most significant surface plasmon response and red-shift of the resonance absorption peak appeared. Meanwhile, short circuit current density of the device increased from 9.93 mA/cm² to 12.98 mA/cm², the fill factor increased from 49.35% to 52.79% and the power conversion efficiency increased from 3.05% to 4.01%. These results provided a theoretical guidance to optimize the design and increase the performance of solar cells.     

折射率色散效应对晶体硅太阳电池反射率的影响

为了分析色散效应对晶体硅太阳电池反射率的影响,在考虑材料折射率色散效应的情况下,运用光学干涉矩阵计算了具有SiO2单层减反射膜和MgF2/ZnS双层减反射膜晶体硅太阳电池的反射率与波长的函数关系,并与实验结果和未考虑色散效应的计算结果进行了对比分析.结果表明：考虑折射率色散效应的计算结果与实验测量数据完全相符,而未考虑折射率色散效应的计算结果与实验测量数据相差较大,最大差值分别为21.5％和16.9％.     

Modeling light trapping and electronic transport of waffle-shaped crystalline thin-film Si solar cells

Monocrystalline Si films from the novel perforated-Si process are candidates for the fabrication of thin-film solar cells because their waffle shape enhances the optical absorption and hence permits the use of films with a thickness of only a few microns. We study the optics of waffle cells by three-dimensional Monte Carlo ray-tracing. A high photogeneration of 38 mA/cm² from a film of thickness W_f=4 μm is possible due to a detached Al-back surface reflector that has an effective reflectance of 99.7% at 1250 nm. Our analytical model for light trapping in thin films explains this high reflectance. Two-dimensional numerical transport modeling reveals the existence of an optimum texture period p≈2W_f that originates from a carrier collection efficiency that increases with texture period while the photogeneration decreases with period. For well-passivated cells the optimum thickness W_f is at least one fifth of the diffusion length L. Efficiencies of 17% to 18% are feasible with waffle films of 1 to 3 μm in thickness. We introduce an analytic model for the minority carrier transport that agrees with two-dimensional numerical modeling to within 10% and reduces the computation time by orders of magnitude. This analytic model is also applicable to conformal thin-film geometries differing from the waffle geometry. Received: 1 March 1999 / Accepted: 28 March 1999 / Published online: 24 June 1999     

Nanoroughness control of Al-Doped ZnO for high efficiency Si thin-film solar cells

The Al-doped ZnO (ZnO:Al) front transparent conducting oxide (TCO) for high efficiency Si thin-film solar cell has been developed using RF magnetron sputtering deposition and chemical wet etching. Microscopic surface roughness of the as-deposited ZnO:Al film estimated by spectroscopic ellipsometry is closely related to the compactness of the TCO film, and shown to be a straightforward and powerful tool to optimize the deposition conditions for the proper post-etched surface morphology. Wet-etching time is adjusted to form the U-shaped craters on the surface of the ZnO:Al film without sharp etch pits that can cause the crack-like defects in the overgrown microcrystalline Si-absorbing layers, and deteriorate the V_oc and FF of the Si thin-film solar cells. That is to say, the nanoroughness control of the as-deposited TCO film with proper chemical etching is the key optimization factor for the efficiency of the solar cell. The a-Si:H/a-SiGe:H/μc-Si:H triple junction Si thin-film solar cells grown on the optimized ZnO:Al front TCO with anti-reflection coatings show higher than 14% conversion efficiency.     

Enhanced performance of InGaN/GaN multiple quantum well solar cells with double indium content

The performance of a multiple quantum well （MQW） InGaN solar cell with double indium content is investigated. It is found that the adoption of a double indium structure can effectively broaden the spectral response of the external quantum efficiencies and optimize the overall performance of the solar cell. Under AM1.5G illumination, the short-circuit current density （Jsc） and conversion efficiency of the solar cell are enhanced by 65% and 13% compared with those of a normal single-indium-content MQW solar cell. These improvements are mainly attributed to the expansion of the absorption spectrum and better extraction efficiency of the photon-generated carriers induced by higher polarization.     

一种新方法制备硅/聚(3, 4-乙撑二氧噻吩)核/壳纳米线阵列杂化太阳能电池

采用气相聚合法制备了有机/无机杂化的硅/聚3, 4-乙撑二氧噻吩核/壳纳米线阵列(SiNWs/PEDOT)太阳能电池. 相对平面结构Si/PEDOT太阳能电池, SiNWs/PEDOT太阳能电池的能量转换效率提升了7倍, 达到3.23%.对比分析反射光谱、I-V曲线及外量子效率的实验结果, 发现SiNWs/PEDOT太阳能电池性能改进的主要原因可归结为: 气相聚合法能够有效地制备出SiNWs/PEDOT电池的核/壳纳米线阵列结构, 使得器件具有高光捕获、高比结面积和高电荷收集效率. 关键词： Si/PEDOT核/壳纳米线结构 太阳能电池 气相聚合     

High-temperature processing of crystalline silicon thin-film solar cells

The crystalline silicon thin-film solar cell combines, in principle, the advantages of crystalline silicon wafer-based solar cells and of thin-film solar cell technologies. Its efficiency potential is the highest of all thin-film cells. In the “high-temperature approach” thin silicon layers are deposited on substrates that withstand processing temperatures higher than 1000 °C. The basic features of the high-temperature crystalline silicon thin-film cell technology are described and some important results are discussed. Received: 1 March 1999 / Accepted: 28 March 1999 / Published online: 24 June 1999     

Highly crystallized sputtered silicon with textured morphology for thin-film solar cells

A light-trapping structure with textured morphology for thin-film solar cell is demonstrated in this paper. It is fabricated through Al evaporation, and has a root-mean-roughness (Rms) of about 120 nm and lateral width of about 1 μm for single bulge. A Mo layer is introduced to be a barrier layer. Subsequently sputtered amorphous silicon film is 100% crystallized by Cu induced crystallization. Reflectivity of samples with different silicon thickness is studied to reveal the light-trapping efficiency and the reflectivity as low as 10% is obtained with only 840 nm thick silicon film. This is a low-cost structure promising for future thin-film solar cells with high efficiency.     

Advantages of InGaN/GaN multiple quantum well solar cells with stepped-thickness quantum wells

InGaN/GaN multiple quantum well (MQW) solar cells with stepped-thickness quantum wells (SQW) are designed and grown by metal-organic chemical vapor deposition. The stepped-thickness quantum wells structure, in which the well thickness becomes smaller and smaller along the growth direction, reveals better crystalline quality and better spectral overlap with the solar spectrum. Consequently, the short-circuit current density (Jsc) and conversion efficiency of the solar cell are enhanced by 27.12% and 56.41% compared with the conventional structure under illumination of AM1.5G (100 mW/cm2). In addition, approaches to further promote the performance of InGaN/GaN multiple quantum well solar cells are discussed and presented.