Quantum dot-modified CsPbIBr2 perovskite absorber for efficient and stable photovoltaics

Halide CsPbX3 perovskites, superior photovoltaic materials with great thermal endurance, are of tremendous passion for tunable bandgaps and gratifying applications in colored-light-emitting diodes (LEDs) and tandem solar cells (TSCs). Nevertheless, the inferior moisture tolerance for cubic (α)-phase perovskite is still a huge obstacle for sustaining output of CsPbX3-based perovskite solar cells (PSCs) under ambient pressure. For the representative CsPbIBr2 perovskite, the solution-derived film, enduring the disappointing quality for the existing voids and pinholes, severely limits its device performance and long-time outputs. Herein, we introduced a perovskite surface modification method, overspreading anion-exchanged CsPbIBr2 alloy quantum dots (QDs) over the bulk materials, to protect interior CsPbIBr2 perovskites by moisture isolation. As a reward, this attempt can help the thin perovskite films and associated devices against the ambient environments to achieve a superior stability, as well as a gratifying efficiency improvement of ~12% (8.16% vs. 7.31%) due to the defect passivation. Particularly, the QDs-modified perovskite films can still remain ~78% absorption after a two-stage storage of low humidity (~36%) and high humidity (~80%), comparing with a complete phase transformation (α → β) of the conventional films.