Cu(In,Ga)Se2 Solar Cells With Amorphous Oxide Semiconducting Buffer Layers

A transparent amorphous oxide semiconductor (TAOS) layer for the suppression of interface recombination and enhancement of open-circuit voltage (V_oc) in Cu(In,Ga)Se₂ (CIGS) solar cells is demonstrated. A 60-nm-thick n-type a-In_2-2xGa_2xO₃ (x = 0.6, 0.7, 0.8, 0.9, 1)or a-Ga_2-2yAl_2yO₃ (y = 0.1, 0.2) layer was introduced between the CIGS film and the ZnO transparent front contact. The solar cell performance systematically varied as a function of x and y, and CIGS solar cells with a-In_2-2xGa_2xO₃ (x = 0.9, 1) buffer layers showed V_oc values comparable with those of a reference cell with standard i-ZnO/CdS buffer layers. Current density-voltage (J-V) curve behavior can be explained by conduction band discontinuity at the TAOS/CIGS interface and the carrier density of the TAOS layer.