Stabilization of PN heterojunction between Cu(InGa)Se-2 thin-film absorberand ZnO window with Zn(O, S, OH)(x) buffer

Dramatic improvement of current-voltage (I-V) performance, especially the f ill factor (FF) observed in the Cu(InGa)Se-2-based thin-film circuits with Zn(O, S, OH)(x) buffer after postdeposition light soaking is discussed in t his study. Considering the composition of Zn(O, S, OH)(x) buffer and the re versible behavior with respect to postdeposition light soaking, a model is proposed, in which H2O molecules released by the dehydration of Zn(OH)(2) i n the Zn(O, S,OH)(x) buffer are considered to play a dominant role in this behavior. Based upon this model, attempts to stabilize the pn heterojunctio n by making the reversible behavior irreversible are, for the first time, s uccessfully achieved by adjusting the postdeposition light-soaking conditio ns. The reduction of the Zn(OH)(2) concentration in the Zn(O, S, OH)(x) buf fer through the combination of heating at 130 degrees C for at least 40 min and irradiation using a constant-light solar simulator contributes to stab ilizing the pn heterojunction and improving the I-V performance as well as the electrical yield.