Surface Bridging and Passivation of Homogenized Perovskite Nanograins for Efficient and Stable Pure Green Light‐Emitting Diodes

Quasi‐2D perovskites have demonstrated significant potential for applications in perovskite light‐emitting diodes (PeLEDs). However, issues such as nonradiative recombination induced by defects, energy transfer losses caused by disordered phase distribution, and carrier transport limitation imposed by grain boundary barriers severely hinder the realization of high‐performance PeLEDs. Here, a dual‐additive synergistic strategy is reported that successfully passivates surface defects, shortens intergranular distance, and optimizes phase homogenization of perovskite nanograins in the formamidinium (FA)‐based quasi‐2D perovskite films. The additives of diphenyl(2,4,6‐trimethylbenzoyl)phosphine oxide (DTBPPO) and tris(4‐fluorophenyl)phosphine oxide (TFPPO) are introduced into the precursor solution and anti‐solvent, respectively. DTBPPO is found to anchor adjacent nanograins via C = O and P = O bidentate coordination to reduce the spacing between nanograins and enhance carrier transport. TFPPO is demonstrated to slow down the crystallization rate through hydrogen bonding between fluorine atoms and organic cations, suppressing low‐n phases and promoting energy transfer. Both DTBPPO and TFPPO passivate the surface defects of perovskite nanograins, effectively reducing non‐radiative recombination losses. Ultimately, the dual‐additive synergistic effects yield pure green PeLEDs for Rec. 2020 compliance, with maximum external quantum efficiency of 24.41% and prolonged operational lifetime. The collaborative paradigm of “nanograin bridging‐phase homogenization‐defect passivation” provides new insights for developing high‐performance perovskite optoelectronic devices.