CsPbBr 3 Quantum Dots Incorporation as a Strategy to Mitigate Surface and Grain Boundary Defects in FAPbI 3 Perovskite Solar Cells

The defect passivation strategy for the fabrication of formamidinium lead iodide (FAPI) perovskite thin films is developed by incorporating CsPbBr 3 perovskite quantum dots (CPB QDs) via an antisolvent‐assisted technique. The CPB QDs effectively passivate the defects by interacting with uncoordinated Pb 2+ ions on the surface and at grain boundaries, leading to the formation of high‐quality FAPI thin films. The effect of various sizes of the CPB QDs on the morphology and device performance was also studied. The CPB QD‐modified FAPI films exhibit enhanced photoluminescence intensity and prolonged carrier lifetimes, indicating reduced nonradiative recombination at the interface. Furthermore, the stability of the films is evaluated under ambient conditions over 20 days, with sequential X‐ray diffraction analysis confirming their excellent phase stability. X‐ray photoelectron spectroscopy confirmed the presence of CPB QDs on the surface of the FAPI thin films. The perovskite solar cells fabricated with mesoporous n‐i‐p architecture incorporating CPB QDs achieve a power conversion efficiency of 17.44%, with an open‐circuit voltage ( V oc ) of 1.087 V, short‐circuit current density ( J sc ) of 23.70 mA cm −2 , and fill factor of 67.7%, significantly outperforming pristine FAPI devices. Additionally, the modified device demonstrates excellent stability, retaining 85% of its initial efficiency after 20 days under ambient conditions.