Double‐Layer Quantum Dots as Interfacial Layer to Enhance the Performance of CsPbI3 Solar Cells

Abstract CsPbI 3 has drawn constant interest in the field of perovskite solar cells (PSCs), due to its remarkable photovoltaic performance and thermal stability. Nonetheless, further development of CsPbI 3 PSCs requires solving larger energy loss problem, which is primarily caused by charge recombination and energy band mismatch at the interface. Here, a double‐layer interface engineering concept is introduced that uses CsPbBr 3 and CsPbCl 3 colloidal quantum dots (QDs) to reduce energy loss. Characterization results suggest that the QDs interfacial layer not only improves the quality of CsPbI 3 film through passivating the defects on the film surface and grain boundaries (GBs), but also optimizes energy level structure and establishes additional charge transport paths to facilitate hole transportation. As a result, the power conversion efficiency (PCE) of the device with double‐layer QDs covering is boosted to 18.89% from 17.26%. Its moisture stability is enhanced as well. This work of designing double‐layer QDs provides a new idea for interface engineering, and further manifests the great potential of QDs as interfacial layer.