Engineering of perovskite light-emitting diodes based on quasi-2D perovskites formed by diamine cations

Thus far, most of the layered quasi-2D perovskite materials exploited in the perovskite light-emitting diodes (PeLEDs) are based on large-size monoamine cations, which forms a bilayered organic barrier between the perovskite sheets (known as the Ruddlesden-Popper (RP) phase). However, the organic spacer between the perovskite sheets can be composed of a single-layer diamine cation, for which the perovskite sheets might possess a strengthened connection due to the direct linkage of the diamine cation (referred as the Dion-Jacobson (DJ) phase). Until now, the studies of PeLEDs based on the DJ phase 2D perovskite materials are still rare. Herein, a series of DJ phase quasi-2D EDBE(MAPbBr₃)_n-1PbBr₄ perovskites [EDBE: 2,2-(ethylenedioxy)bis(ethylammonium)] is developed and their application in PeLEDs is investigated. Interestingly, different to the broad emission of the 2D EDBEPbBr₄ film, the quasi-2D film exhibited a narrow emission, indicating a decreased lattice torsion and trap states. After careful device engineering, a green light-emitting perovskite LED based on the EDBE(MAPbBr₃)₂PbBr₄ film is demonstrated to deliver a maximum luminescence of 1903 cd m⁻² and a maximum EQE of 1.06%. We note such performance is inferior to the existing RP phase 2D perovskite, which is limited by the poor thermal stability of the studied EDBE-based 2D perovskites.