Efficient flexible Mo foil-based Cu2ZnSn(S, Se)4 solar cells from In-doping technique

Abstract

Cation substitution has an important impact on the power conversion efficiency (PCE) of Cu2ZnSn(S,Se)4 (CZTSSe) solar cells. Herein, a significant PCE enhancement of flexible indium-doped CZTSSe solar cells has been achieved by partially substituting Sn4+ with In3+. Systematic measurements indicate that In doping in CZTSSe film effectively improves the crystallinity and carrier concentration of the absorber layer. Meanwhile, the treatment reduces interface recombination and band tailing by passivating deep defects and increases the open-circuit voltage (Voc) of the solar cells. By physical analysis, the key parameters for the solar cell diode such as A, J0, Rs and Rsh are significantly improved after In-doping, indicating better PN junction quality. Under the optimal In-doping (x = In/(Sn + In) = 9%), the flexible Cu2ZnSn1-xInx(S,Se)4 solar cell has been successfully obtained with the best efficiency of 7.19% and the Voc enhancement of 62 mV due to reduced Voc deficit and band tailing.