Screening Fluorination Additives for Efficient Perovskite Light‐Emitting Diodes

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.