摘要/Abstract
铜锌锡硫硒(CZTSSe)电池具有组成元素丰度高且环境友好、光吸收系数高、带隙可调、高稳定性等优点, 是一类非常有发展前景的新型薄膜太阳能电池. 目前, CZTSSe电池最高认证效率为12.6%, 与商品化铜铟镓硒(CIGS)电池相比仍然有较大差距, 特别是开路电压(VOC)和填充因子(FF)偏低. 开压损耗是制约CZTSSe器件效率进一步提升的关键因素之一. 其中, 吸收层带尾态和深能级缺陷及界面能级不匹配是开压损耗大的主因, 而Cu-Zn无序引起的铜锌替位(CuZn)与锌锡替位(SnZn)缺陷又是影响带尾态的关键因素, 因此, 减少CuZn和SnZn缺陷有助于提升VOC. 一价金属替位能有效改善带尾态、构建合适能带结构, 在一定程度上解决器件开压损耗问题. 但是, 有关一价金属替位如何影响CZTSSe电池性能, 仍然缺乏全面系统的概述. 本文综述了基于一价金属替位方法CZTSSe电池的研究进展. 首先介绍CZTSSe电池的发展历程、工作原理、制备工艺和关键材料等; 其次, 详细讨论一价金属替位的理论研究; 再次, 结合实验进展, 重点讨论一价金属部分替位及完全替位CZTSSe材料的制备及其对带尾态、界面缺陷和能带结构研究; 最后, 对一价金属替位研究的关键科学问题、未来发展潜力等进行讨论和展望, 并提出可能的解决思路.
关键词: 铜锌锡硫硒, CuZn反位缺陷, 一价金属替位, 晶体生长, 带尾态
Cu2ZnSn(S,Se)4 solar cell (CZTSSe), as a new type of inorganic thin-film solar cells, has been widely studied in recent years due to the advantages of earth-abundant and environmental-friendly composition elements, high light absorption coefficient and adjustable band gap. CZTSSe solar cell is thus a highly competitive photovoltaic device with potential applications in flexibility, building integrated photovoltaics (BIPV) and so on. So far, 12.6% certified efficiency has been achieved for this kind of solar cells. Open-circuit voltage (VOC) deficit is always the key factor to unsatisfied efficiency of CZTSSe solar cells, and band tailing, mismatch of energy band structure and deep level defects are the main causes to VOC deficit. Typically, Cu-Zn disorder-induced defects widely exist in the bulk absorber, due to similar radius of Cu and Zn elements could lead to relatively low formation energy of CuZn and ZnCu anti-site defects. Metal(I) substitution is an effective way to solve Cu-Zn disorder, which can well reduce VOC deficit via lowering band tailing and improving the device structure, leading to better cell performance. However, very few review papers have focused on the metal(I) substitution work. In this review, we will summarize the research progress of metal(I) substitution in Cu2ZnSn(S,Se)4 thin film solar cells. Part I introduces the structure and problems of CZTSSe solar cells. Part II shows the origin of metal(I) substitution and theoretical research on substituted materials. Part III focuses on synthetic methods about metal(I) partial substitution devices and influence on crystal growth, band tailing, interface defects and band structure. Part IV briefly introduces metal(I) total substitution devices. Part V anticipates the prospects and bottleneck of metal(I) substitution devices, and give some possible solutions to these current issues.
Key words: Cu2ZnSn(S,Se)4, CuZn anti-site defects, metal(I) substitution, crystal growth, band tailing
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