Fine-Modulation of Perovskite Ion-Additive Binding Interaction Using Multidentate Ligation for High Performance Perovskite Light-Emitting Diodes

Research on perovskite light-emitting diodes (PeLEDs) has primarily focused on modulating crystal growth to achieve smaller grain sizes and defect passivation using organic additives. However, challenges remain in controlling the intermolecular interactions between these organic additives and perovskite precursor ions for precise modulation of crystal growth. In this study, we synthesize two triphenylphosphine oxide (TPPO)-based multidentate additives: bidentate hexane-1,6-diyl-bis(oxy-4-triphenylphosphine oxide) (2-TPPO) and tetradentate pentaerythrityl-tetrakis(oxy-4-triphenylphosphine oxide) (4-TPPO). We investigate the crystallization of perovskites through real-time crystal growth analyses and theoretical calculations. As the extent of multidentate binding increases, perovskite crystallization slows down gradually. The multidentate TPPO additives exhibit strong binding to Pb²⁺ ions through multidentate ligation in the precursor solution, leading to retarded halide-mediated crystal growth, reduced crystallite size, and enhanced exciton binding energy. Moreover, these multidentate additives reduce trap-mediated nonradiative losses by forming stronger multiple bonds with undercoordinated Pb²⁺ defects in perovskite films, while also promoting effective strain relaxation. The synergistic effects of the multifunctional and multidentate 4-TPPO additive result in highly efficient PeLEDs, with a maximum current efficiency of 81.12 cd A^-1 and a maximum external quantum efficiency of 25.19%. Our findings demonstrate the successful manipulation of crystallization dynamics through the control of additive and Pb²⁺ multidentate binding interactions, presenting an effective strategy for application-specific crystal growth.