High-efficiency Cu(In,Ga)Se2 thin-film solar cells with a novel In(OH)3:Zn2+ buffer layer

We propose the inclusion of a novel In(OH)3:Zn2+ buffer layer for fabricating high-efficiency CIGS solar cells. This buffer layer was deposited using a solution consisting of ZnCl2, InCl3·4H2O, and thiourea. The In(OH)3:Zn2+ films showed high resistivities of 2.1×108 Ω cm and transmittance of above 95% in the visible range. We expected two effects due to this new buffer layer: first is the formation of a passivation layer on the CIGS surface and the second is Zn-doping into CIGS layer, resulting in the formation of a buried junction. A cell efficiency of 14.0% (Voc: 0.575 V, Jsc: 32.1 mA/cm2, FF: 0.758) was achieved by using an In(OH)3:Zn2+ buffer layer, without the light soaking effect.