Research on conduction band offset of CZTSSe solar cell with double absorber layers

Abstract

Cu₂ZnSn(S,Se)₄ (CZTSSe) is considered to be the most potential light-absorbing material to replace CuInGaSe₂ (CIGS), but the actual photoelectric conversion efficiency of such cells is much lower than that of CIGS. One of the reasons is the high recombination rate of carriers at the interface. In this paper, in order to reduce the carrier recombination, a new solar cell structure with double absorber layers of Al-doped ZnO (AZO)/intrinsic (i)-ZnO/CdS/CZTS _x1Se_1−x1 (CZTSSe₁)/CZTS _x2Se_1−x2 (CZTSSe₂)/Mo was proposed, and the optimal conduction band offsets (CBOs) of CdS/CZTSSe₁ interface and CZTSSe₁/CZTSSe₂ interface were determined by changing the S ratio in CZTSSe₁ and CZTSSe₂, and the effect of thickness of CZTSSe₁ on the performance of the cell was studied. The efficiencies of the optimized single and double absorber layers reached 17.97% and 23.4%, respectively. Compared with the single absorber layer structure, the proposed structure with double absorber layers has better cell performance.

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Tianjin University of Technology