Efficient Cu(In,Ga)(Se,S)2 modules with sputtered Zn(O,S) buffer layer

We demonstrate that a simple and low-cost industrial sputter process can be used to substitute the InxSy:Na buffer and intrinsic ZnO layer with a single film of Zn(O,S). Cu(In,Ga)(Se,S)2 (CIGS) modules with an aperture area of 667 cm2 and efficiencies up to 15.6% were prepared using a sputtered Zn(O,S) buffer layer. In comparison with our InxSy:Na reference, Zn(O,S) modules exhibit a superior short-circuit current which is overcompensated by a loss in the open-circuit voltage. The quality of the Zn(O,S)/CIGS interface, as judged from saturation current density and ideality factor, is close to that of the InxSy:Na reference. Electroluminescence images demonstrate a low and uniform recombination across the active module area. In first experiments, damp heat tests reveal a degradation in conversion efficiency of 4-6% relative. Hence, if the interface properties can be improved by further process optimization, the sputtered Zn(O,S) buffer is a promising candidate to increase the efficiency and reduce the costs of CIGS modules.