Influence of absorber layer gradual gap profile on Cu₂ZnSn(S_1-Y Se_Y )₄ solar cell efficiency: Numerical study

Abstract

The gradual substitution of sulfur atoms (S) by selenium atoms (Se) in Cu₂ZnSn(S_1-y Se_y )₄ compounds causes a linear increase in the optical band-gap. For this reason, those compounds are suitable to implement band-gap engineering in compositionally graded solar cells. In this paper, we have worked to take advantage of this feature to enhance the performances of the basic uniform Kesterite and Stannite CZTS_1–ySe_y solar cells. The influence of Tow grading profile was investigated: fully graded (a) and double graded (b). Fully graded Cell showed better parameters than compositionally uniform cells. In Double graded cells it appeared that front grading had a disruptive effect on solar cell parameters. In contrary back grading ameliorates significantly all cell parameters. As a result, the efficiency of kesterite and stannite cells was enhanced from 9.05 and 5.22% to 16.65 and 15.77 % respectively.