Fine-Modulation\nof Perovskite Ion-Additive Binding\nInteraction Using Multidentate Ligation for High Performance Perovskite\nLight-Emitting Diodes

Research on perovskite light-emitting diodes (PeLEDs)\nhas primarily\nfocused on modulating crystal growth to achieve smaller grain sizes\nand defect passivation using organic additives. However, challenges\nremain in controlling the intermolecular interactions between these\norganic additives and perovskite precursor ions for precise modulation\nof crystal growth. In this study, we synthesize two triphenylphosphine\noxide (TPPO)-based multidentate additives: bidentate hexane-1,6-diyl-bis(oxy-4-triphenylphosphine\noxide) (2-TPPO) and tetradentate pentaerythrityl-tetrakis(oxy-4-triphenylphosphine\noxide) (4-TPPO). We investigate the crystallization of perovskites\nthrough real-time crystal growth analyses and theoretical calculations.\nAs the extent of multidentate binding increases, perovskite crystallization\nslows down gradually. The multidentate TPPO additives exhibit strong\nbinding to Pb<sup>2+</sup> ions through multidentate ligation in the\nprecursor solution, leading to retarded halide-mediated crystal growth,\nreduced crystallite size, and enhanced exciton binding energy. Moreover,\nthese multidentate additives reduce trap-mediated nonradiative losses\nby forming stronger multiple bonds with undercoordinated Pb<sup>2+</sup> defects in perovskite films, while also promoting effective strain\nrelaxation. The synergistic effects of the multifunctional and multidentate\n4-TPPO additive result in highly efficient PeLEDs, with a maximum\ncurrent efficiency of 81.12 cd A<sup>–1</sup> and a maximum\nexternal quantum efficiency of 25.19%. Our findings demonstrate the\nsuccessful manipulation of crystallization dynamics through the control\nof additive and Pb<sup>2+</sup> multidentate binding interactions,\npresenting an effective strategy for application-specific crystal\ngrowth.