Experimental evidence of light soaking effect in Cd-free Cu2ZnSn(S,Se)4-based solar cells

The use of a Zn-based buffer layer for kesterite solar cells presents the double advantage of avoiding cadmium and reducing the amount of light absorbed in this layer. Cu2ZnSn(S,Se)4 solar cells with a ZnS(O,OH) buffer layer have been fabricated and power conversion efficiencies up to 5.8% after light soaking treatment have been measured. Cu2ZnSn(Se,S)4 solar cells with a CdS buffer layer have also been realized, leading to a power conversion efficiency up to 7.0%. The dynamics of the light soaking effect in the case of the ZnS(O,OH) buffer layer has been studied as well, and compared to the same effect on a cell with a Cu(In,Ga)Se2 absorber layer. •5.8% of efficiency for a Cu2ZnSn(S,Se)4 solar cell with a ZnS(O,OH) buffer layer•7.0% of efficiency for a reference Cu2ZnSn(S,Se)4 solar cell with a CdS buffer layer•ZnS(O,OH) buffer layer required at least 1000min of light soaking treatment.•Required light soaking treatment is longer for Cu2ZnSn(S,Se)4 than for Cu(In,Ga)Se2.