Solution‐Mediated Hybrid FAPbI₃ Perovskite Quantum Dots for Over 15% Efficient Solar Cell

Abstract Organic–inorganic formamidinium lead triiodide (FAPbI₃) hybrid perovskite quantum dot (QD) is of great interest to photovoltaic (PV) community due to its narrow band gap, higher ambient stability, and long carrier lifetime. However, the surface ligand management of FAPbI₃ QD is still a key hurdle that impedes the design of high‐efficiency solar cells. Herein, this study first develops a solution‐mediated ligand exchange (SMLE) for preparing FAPbI₃ QD film with enhanced electronic coupling. By dissolving optimal methylammonium iodide (MAI) into antisolvent to treat the FAPbI₃ QD solution, the SMLE can not only effectively replace the long‐chain ligands, but also passivate the A‐ and X‐site vacancies. By combining experimental and theoretical results, this study demonstrates that the SMLE engineered FAPbI₃ QD exhibits lower defect density, which is beneficial for fabricating high‐quality QD arrays with desired morphology and carrier transport. Consequently, the SMLE FAPbI₃ QD based solar cell outputs a champion efficiency of 15.10% together with improved long‐term ambient storage stability, which is currently the highest reported value for hybrid perovskite QD solar cells. These results would provide new design principle of hybrid perovskite QDs toward high‐performance optoelectronic application.