In Situ Ligand Bonding Management of CsPbI₃ Perovskite Quantum Dots Enables High‐Performance Photovoltaics and Red Light‐Emitting Diodes

To fine-tune surface ligands towards high-performance devices, we developed an in situ passivation process for all-inorganic cesium lead iodide (CsPbI₃ ) perovskite quantum dots (QDs) by using a bifunctional ligand, L-phenylalanine (L-PHE). Through the addition of this ligand into the precursor solution during synthesis, the in situ treated CsPbI₃ QDs display significantly reduced surface states, increased vacancy formation energy, higher photoluminescence quantum yields, and much improved stability. Consequently, the L-PHE passivated CsPbI₃ QDs enabled the realization of QD solar cells with an optimal efficiency of 14.62 % and red light-emitting diodes (LEDs) with a highest external quantum efficiency (EQE) of 10.21 %, respectively, demonstrating the great potential of ligand bonding management in improving the optoelectronic properties of solution-processed perovskite QDs.