Chu Liangli, Zhang Jinping, Xiang Huiwen, Wu Sixin, Jia Yu, Liu Chengyan
Henan Key Laboratory of Photovoltaic Materials, Key Laboratory for Special Functional Materials of Ministry of Education, and The Joint Center for Theoretical Physics, Henan University, Kaifeng 475004, People's Republic of China.
Faculty of Engineering, Huanghe Science and Technology College, Zhengzhou 450006, People's Republic of China.
Inorg Chem. 2022 Aug 8;61(31):12293-12300. doi: 10.1021/acs.inorgchem.2c01575. Epub 2022 Jul 27.
The inferior electrical properties at the interface of the CuZnSnS/CdS (CZTS/CdS) heterojunction resulting in the severe loss of open-circuit voltage () highly restrict the photovoltaic efficiency of CZTS solar cell devices. Here, first-principles calculations show that the Zn-alloyed CdS buffer layer reverses the unfavorable cliff-like conduction band offset (CBO) of CZTS/CdS to the desirable spike-like CBO of CZTS/ZnCdS, which suppresses carrier nonradiative recombination and blocks electron backflow. In addition, the weakened n-type conductivity of ZnCdS can be enhanced by In, Ga, and Cl doping without the introduction of detrimental deep-level defects and severe band-tail states, which improves the of CZTS solar cells by promoting strong band bending and large quasi-Fermi-level splitting at the absorber side of the CZTS/ZnCdS heterojunction. This study finds that the synergetic effects of Zn alloying and defect engineering on the CdS buffer layer are promising for overcoming the long-standing issue of the deficit in CZTS solar cells, and understanding the optimized interfacial electrical properties provides theoretical guidance for improving the efficiency of semiconductor devices.
CuZnSnS/CdS（CZTS/CdS）异质结界面处较差的电学性能导致开路电压（）严重损失，这极大地限制了CZTS太阳能电池器件的光电转换效率。在此，第一性原理计算表明，Zn合金化的CdS缓冲层将CZTS/CdS不利的悬崖状导带偏移（CBO）转变为CZTS/ZnCdS所需的尖峰状CBO，这抑制了载流子的非辐射复合并阻止了电子回流。此外，ZnCdS减弱的n型导电性可通过In、Ga和Cl掺杂得到增强，而不会引入有害的深能级缺陷和严重的带尾态，这通过促进CZTS/ZnCdS异质结吸收体一侧的强能带弯曲和大的准费米能级分裂来提高CZTS太阳能电池的开路电压。本研究发现，Zn合金化和缺陷工程对CdS缓冲层的协同效应有望克服CZTS太阳能电池中长期存在的开路电压不足问题，并且理解优化的界面电学性能为提高半导体器件效率提供了理论指导。
