Revealing oxygen effect on efficiency and stability of quantum dot photovoltaics

Colloidal quantum dot solar cells (CQDSCs) have received great attention in the development of scalable and stable photovoltaic devices. Despite the high power-conversion-efficiency (PCE) reported, stability investigations are still limited and the exact degradation mechanisms of CQDSCs remain unclear under different atmosphere conditions. In this study, the atmospheric influence on the ZnO electron transport layer material (ETL), halide-passivated lead sulfide CQDs (PbS-PbI₂) photoactive layer material and 1,2-ethanedithiol-PbS CQDs (PbS-EDT) hole transport material on device stability in PbS CQDSCs is investigated. It was found that O₂ had negligible influence on PbS-PbI₂, but it did induce the increase in work function of ZnO ETL and PbS-EDT layers. Notably, the increase of the ZnO work function (WF_ZnO) induces the formation of interface barrier between ZnO and PbS-PbI₂, leading to a deterioration in device efficiency. By further replacing ZnO ETL with SnO₂, a multi-interface collaborative CQDSC was constructed to realize the PCE with high stability. This study identifies the efficiency evolution that is inherent in CQDSCs under different atmospheric conditions.