Effects of combined heat and light soaking on device performance of Cu(In,Ga)Se-2 solar cells with ZnS(O,OH) buffer layer

The impacts of air annealing, light soaking (LS), and heat-light soaking (HLS) on cell performances were investigated for ZnS(O,OH)/Cu(In,Ga)Se-2 (CIGS) thin-film solar cells. It was found that the HLS post-treatment, a combination of LS and air annealing at 130 degrees C, is the most effective process for improving the cell performances of ZnS(O,OH)/CIGS devices. The best solar cell yielded a total area efficiency of 18.4% after the HLS post-treatment. X-ray photoelectron spectroscopy showed that the improved cell performance was attributable to the decreased S/(S+O) atomic ratio, not only in the surface region but also the interface region between the ZnS(O,OH) and CIGS layers, implying the shift to an adequate conduction-band offset at the ZnS(O,OH)/CIGS interface. Copyright (c) 2013 John Wiley & Sons, Ltd.