Realizing solution-processed monolithic PbS QDs/perovskite tandem solar cells with high UV stability

Abstract

Among solution-processed photovoltaic materials, lead sulfide (PbS) colloidal quantum dots (QDs) possess a highly tunable bandgap and strong infrared absorption, while metal halide perovskites show extraordinary external quantum efficiency (EQE) in the visible region, which offers the opportunity to construct an ideal tandem cell of PbS QDs/perovskite. However, it still remains a huge challenge to integrate fragile perovskite films into a monolithic tandem structure. We have for the first time addressed the challenge of preparing stable and efficient tandem solar cells combining PbS colloidal QDs with emerging MAPbI₃ perovskites by all-solution-processing. A perfectly superimposed open circuit voltage and an optimal power conversion efficiency (PCE) of 11.03% have been achieved, which is the highest reported PCE for any PbS QD based tandem solar cell. And we believe this efficiency will be further improved by using perovskites with wider bandgaps to provide more complementary absorption. In addition, the introduction of a PbS subcell can effectively eliminate the hysteresis-effect in metal-halide perovskites, and result in high UV stability and exceptional storage stability under a dry environment without encapsulation. Therefore, we revealed that the synergetic use of QDs and perovskite materials in tandem structures can extend the range of device photo response and simultaneously deliver excellent device performance as well as improved stability. Moreover, our work provided an important starting point for future advances in efficient QDs/perovskite tandem solar cells with more complementary absorption.