Effects of combined heat and light soaking on device performance of Cu(In,Ga)Se₂ solar cells with ZnS(O,OH) buffer layer

Abstract

ABSTRACT 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 °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 © 2013 John Wiley & Sons, Ltd.