Influence of the Compositional Variation of ZnxCd1−xS (0 ≤ x ≤ 0.45) Buffer on Efficiency of Cu2ZnSnSe4 Solar Cell: A Simulation

Cu
₂
ZnSnSe
₄
(CZTSe) is one of the promising kesterite-type light absorbing materials to produce low cost third generation solar cells but suffers from poor efficiency. To investigate if modification in buffer layer can enhance efficiency, Zn
_x
Cd
_1-x
S alloy is considered as buffer material in this work for a typical CZTSe solar cell structure instead of mostly used CdS material. The composition of the buffer is varied in the range of 0 ≤ x ≤ 0.45 and its influence on the cell efficiency is studied by a comprehensive 1D device simulation for a variety of absorber/buffer interface recombination scenarios and absorber layer bulk defect states. It is found that, the conduction band offsets (CBO) and carrier recombination rates at CZTSe/buffer interface are the key parameters to control efficiency of the solar cells, as the composition of Zn
_x
Cd
_1-x
S is varied.