Regulation of Perovskite Nucleation and Orientated Crystal Growth via In Situ Self‐Crosslinking Polymer for Bright Perovskite Light‐Emitting Diodes

Abstract Hybrid halide perovskite films are becoming increasingly efficient in various applications, but several challenges still remain to be overcome. In this study, thermally polymerized additive N‐vinyl‐2‐pyrrolidone (NVP) is utilized to tune the crystallization and orientation of mixed organo‐metal perovskite films. Using in situ spectroscopy, it is demonstrated that NVP plays a crucial role in prolonging the crystallization process and separating the nucleation and crystal growth by forming an NVP‐precursor intermediate phase. Additionally, the intermediate adduct effectively passivates defects, reduces nonradiative recombination, improves crystallinity, and enhances the transmission of charge carriers. NVP‐containing perovskite light‐emitting diodes (PeLEDs) are subsequently developed that exhibit stable and bright green luminance exceeding 240 000 cd m −2 . These findings provide valuable insights into manipulating the crystallization behavior of mixed organo‐metal perovskite films.