Screening Fluorination Additives for Efficient Perovskite Light‐Emitting Diodes

Abstract Fluorinated additives are proposed to address the issue of domain polydispersity in quasi‐2D perovskites. However, the lack of established screening criteria for these additives necessitates a laborious and costly trial‐and‐error process. Herein, this work explores the behind nature for the first time how various fluorination in fluorinated additives affect domain distribution in quasi‐2D perovskites. The studies reveal that fully fluorinated additives could suppress undesirable low‐dimensional domains, facilitating efficient energy transfer, while partially fluorinated additives adversely cause deteriorated optical properties. The observed trend is ascribed to the molecular dipole moment of the fluorinated additives, offering a reasonable explanation for experimental phenomena that has never been reported before. By employing fully fluorinated additives, the fabricated sky‐blue perovskite light‐emitting diodes (PeLEDs) deliver a peak external quantum efficiency (EQE) of 20.38% (@488 nm), marking as one of the highest efficiencies reported to date. The finding provides a screening criterion for fluorinated additives to realize efficient PeLEDs.