The Development and Application of High-Efficiency Low-Cost Silicon Thin Film Solar Cell
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The Development and Application of High-Efficiency Low-Cost Silicon Thin Film Solar Cell Xueshi Tan, Bingxue Mao, Feng Zhang, Jingjing Yang Hunan Gongchuang Photovoltaic Science and Technology Co.,Ltd, No.1 Hongyuan Road, Baishazhou Industry Park, Hengyang City, Hunan Province, PR China, 421005 ABSTRACT For the industrial application of silicon thin film solar cells, the current focus is on how to realize high-efficiency low-cost production process and minimize light-induced degradation effect, thus effectively reducing the balance-of-system (BOS) costs of system integration. In this paper, a brief introduction based on our development and application in this area is presented, highlighting in the achievement of some layers in a-Si:H/μc-Si:H tandem solar cell by optimizing the property of single layers, such as amorphous intrinsic layer, intermediate reflective layer and microcrystalline intrinsic layer. After transferring the process achievement to the industrial production line, we obtained the low-cost thin-film silicon solar cells with high photovoltaic conversion efficiency of 10.2%. INTRODUCTION As the costs of photovoltaic (PV) products continue to drop in recent years, the BOS percentage of total costs will gradually increase. BOS refers to all components of a PV system other than the modules, including PV system constructing, mounting structures, power conditioner, land, etc. Low voltage designed thin-film silicon solar modules will result in a higher number of modules stringed to the system, which will lower BOS costs by 3% at least; higher efficiency modules mainly benefit from reducing the cost of inverters, and also can effectively reduce BOS costs [1]. In particular for the limitation of mounting area in some cases, high efficiency is even more important. In large scale industrialization, to fabricate high efficient amorphous (a-Si)/microcrystalline (μc-Si) tandem solar cells should consider to increase initial efficiency while keeping the light induced degradation (LID) under control [2], which is the key factor to achieve efficient improvement. According to the study, the properties of absorber layers and buffer layers measured by FTIR have a strong correlation with the degradation of a-Si cells [3]. For the amorphous top cell, the light-induced degradation can be significantly reduced by optimizing PECVD (plasma enhanced chemical vapor deposition) process conditions to obtain high quality intrinsic a-Si absorber. While in tandem solar cells, a silicon oxide based intermediate reflector (SOIR, typically using nano-crystalline material nc-SiOx:H) [4] inserted between the top and bottom cell results in the improvement of the top cell spectral response and makes it more likely to thin the amorphous layer with severe degradation. By tuning the process conditions, the optimization of SOIR thickness, refractive index, and conductivity can be realized. For the microcrystalline bottom cell, the adopted μc-Si thin film is a mixed phase of amorphous phase, microcrystalline grain, boundary and micro-holes. The
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