Behavior of indium alloying with Cu2ZnSn(S,Se)4 and its effect on performances of Cu2ZnSn(S,Se)4-based solar cell

Abstract P-type solid solutions of indium (In) in kesterite Cu 2 ZnSn(S,Se) 4 films (CZTSSe(In)) with In contents of 0–19.34 at% were prepared by In alloying with the kesterite Cu 2 ZnSn(S,Se) 4 (CZTSSe) through a solution approach. It is found that the In substitutes for Sn to form In Sn acceptor defect in the CZTSSe(In) in the In content range of 0–1.15 at%, and for Cu and Sn to form In Cu -In Sn donor complex or/and for a small number of Zn to form In Zn donor defects in the range of 6.34–19.34 at%. The hole concentration of the CZTSSe(In) increases with increasing In content in the range of 0–1.15 at%, but decreases in the range of 6.34–19.34 at%. The bandgap of the CZTSSe(In) increases from 1.040 eV for CZTSSe to 1.083 eV for CZTSSe(In) with 19.34 at% In. Three solar cells with traditional structure and power conversion efficiency (PCE) of 3.52, 3.24 and 1.67% were fabricated by using the CZTSSe and CZTSSe(In) with In content of 0.67 and 12.27 at% as absorbers, respectively. It is found that the effect of the bandgap on the open-circuit voltage (V oc ) is little compared to the hole concentration. The increased hole concentration enhances the V oc but decreases the photogenerated current density (J ph ) and reverse saturation current density (J 0 ). The effect of In alloying on the PCE of the CZTSSe(In)-based solar cell is determined by the effects of the hole concentration on V oc , J ph and J 0 . The influence mechanism of the In alloying on the properties of the CZTSSe and performance of the CZTSSe-based solar cell are discussed in the present work.