Optimizing the properties of Cu2ZnSn(S,Se)4 solar cells via cationic substitution with trace Ca.

Cation substitutions have the significant impact on suppressing the detrimental defects and associated clusters of CZTSSe thin film solar cells. In our work, trace Ca is used to replace Zn to control the cationic disorder in CZTSSe absorber, improving the performance of CZTSSe solar cells. By tuning the amount of Ca doping, the alloyed Cu 2 Ca x Zn 1- x Sn(S,Se) 4 phase can be formed, and the effects of tiny Ca doping on the properties of CZTSSe absorber are studied in detail. After 2% Ca is doped into the precursor solution, the highest efficiency of CZTSSe solar cells can be optimized to 8.73% from 7.06%, and the improvement of V OC is observed from 382 to 417 mV, which both benefit from the reduced formation of the detrimental defects. Our findings also provide the new insights for further improvement of CZTSSe solar cells based on earth abundant elements. • Substitution of Zn with trace Ca can suppress detrimental defects in absorber for 35 mV increase of devices. • Enhanced crystallinity, grain size, and electrical properties of absorber can be observed after Ca incorporation. • The best efficiency of Cu 2 Ca x Zn 1- x Sn(S,Se) 4 device can be obtained to be 8.73% at x = 0.02. [ABSTRACT FROM AUTHOR]