Ga3+和Ge4+共掺杂制备“V”字型带隙结构的高效率Cu2ZnSn(S,Se)4太阳能电池

Cu2ZnSn(S,Se)4 （CZTSSe）被认为是理想的太阳能电池吸光层材料，但是其效率远低于与其类似的铜铟镓硒太阳能电池。CZTSSe太阳能电池效率低的本质原因是其传统的带隙结构和CuZn反位缺陷损耗了电池的开路电压，而且电子和空穴在背电极易发生复合导致短路电流和填充因子偏低。本项目拟通过Ga3+和Ge4+离子共掺杂来构筑双梯度“V”字型带隙结构的CZTSSe吸光层，来形成有利于电子单梯度传输的带隙结构，同时抑制反位缺陷，从而提高电池的开路电压、短路电流和填充因子。Ga3+和Ge4+离子共掺杂充分利用了Ga3+离子的扩散速率慢、Ge4+离子掺杂能够提高CZTSSe的表面带隙并且能够促进晶体生长的三大优势。本项目通过理论分析和设计系统的优化措施，构建“V”字型带隙结构的CZTSSe吸光层，为进一步提高CZTSSe太阳能电池效率提供创新性的解决方案。

Cu2ZnSn(S,Se)4 (CZTSSe) is considered as the ideal material for solar cell absorber layer, but it’s current efficiency is much lower than the CIGSe solar cells. The key factors for limiting the efficiency of CZTSSe solar cells are the loss of open-circuit voltage for the traditional band gap structure and the anti-site defect (CuZn), meanwhile, the short circuit current and fill factor is low for the recombination of electrons and holes in the Mo back electrode. This project mainly targets at fabricating the CZTSSe absorber layers with the double gradient “V” type bandgap structure by Ga3+ and Ge4+ co-doping strategy. The “V” type bandgap structure is conducive to enhance the single gradient electron transport and reduce the adverse defect, and then obviously improve open-circuit voltage, short circuit current and fill factor. Ga3+ and Ge4+ co-doping strategy shows the three advantages of low Ga3+ diffusion rate, improving the band gap of the surface of absorber layer by Ga3+-doping, and enhancing the crystal growth. Through theoretical analysis and systematically optimizing the experimental conditions, we want to fabricate the CZTSSe absorber layers with “V” type bandgap structure, and provide an innovative solution to further improve the efficiency of CZTSSe solar cells.