Interface engineering with ionic liquid for achieving efficient Quasi-2D perovskite light-emitting diodes

Perovskite light-emitting diodes (PeLEDs) have attracted wide attention due to their excellent photoelectric properties. A variety of additives have been studied for perovskite emission layers to enhance the performance of PeLEDs. However, the buried interface, which also has significant influence on the crystallization kinetics and exciton recombination dynamics of the perovskite emission layer, remains to be explored. In this work, we introduced a new ionic liquid 1-Ethyl-3-methylimidazolium dicyanamide (EMIM DCA) with the characteristics of low viscosity and high conductivity into the interfacial layer between the hole transport layer (HTL) and the perovskite film. Due to the strong interaction between the EMIM DCA and perovskite, the crystallization of the perovskite film is obviously improved and the defects at the interface are well passivated. As a result, the nonradiative recombination in the interlayer is significantly reduced. In addition, the introduction of EMIM DCA promoted the injection of charge carriers, thus achieving a high luminance of 32310 cd m(-2) and enabling the maximum external quantum efficiency (EQE) of the PeLEDs increased from 10.2 % to 18.7 %.