Efficient Dion-Jacobson perovskite light-emitting diodes via mixed cation engineering.

Abstract

Quasi-two-dimensional (quasi-2D) perovskites with high exciton binding energy (Eb) can confine carriers to form an energy funnel cascade, accelerate carrier localization to the emitting domain, and decrease nonradiative recombination loss. Herein, it is shown that partially alloying Cs+ cations into formamidinium (FA)-based Dion-Jacobson (DJ) perovskites and adjusting the stoichiometric ratio can simultaneously modify the tolerance factor, decrease the phase formation enthalpy, improve the morphology, modulate the phase distribution, and boost the current efficiency. By incorporating CsBr to substitute for some of the FABr, perovskite films with narrower phase distributions and fewer defects are obtained, and the current efficiency is boosted from 18.2 to 25.3 cd/A. A high current efficiency of 42.1 cd/A, a record (as far as we are aware) external quantum efficiency (EQE) of 10.5%, and a maximum luminance of 18600 cd/m2 with an emission peak at 529 nm are obtained when the Lewis base passivation agent TPBi is dissolved in the antisolvent. This is the first time, to the best of the authors' knowledge, that efficient 1,4-phenyldimethylammonium dibromide (PHDMADBr)-based green-light DJ perovskite light emitting diodes (PeLEDs) based on mixed Cs+ and FA+ cations have been fabricated.