Comparative study of As and Cu doping stability in CdSeTe absorbers

The reasons behind the long-term degradation of Cu-doped CdTe thin-film solar cells have been a topic of dis-cussion for almost two decades. Yet the underlying mechanisms of such degradation, especially interactions of Cu doping with Cl in high-performance CdSeTe devices, still lack detailed understanding. In this study, we provide a consistent theoretical analysis of the fundamental physics behind this phenomenon. We then identify the dominant device degradation mechanism that cannot be completely eliminated in Cu-doped chlorinated CdSeTe-based PV. Finally, we conclude that this key mechanism is absent in CdSeTe PV when using arsenic absorber doping, which explains the remarkable stability demonstrated by this new technology. Theoretical conclusions are supported by the results of accelerated life tests on Cu-and As-doped chlorinated CdSeTe cells.