Ionic-compound based high performance perovskite light emitting diodes

Metal halide perovskite has attracted much attention due to its adjustable color, high color purity, and excellent photoelectric properties. The quality of the perovskite film is one of the key factors that affect the performance of device. Here, PEA₂Cs_<i>n</i>–1Pb_<i>n</i>Br_3<i>n</i>+1 thin films are prepared by directly doping the ionic compound additive tetraphenylphosphine chloride (TPPCl) into the perovskite precursor of the light-emitting layer based on additive assisted technology. High-quality perovskite films with uniform, less pinholes and smaller grains are obtained. Not only is the photoluminescence (PL) performance of PeLEDs improved but the electroluminescence (EL) performance of PeLEDs with a double electron transport layer also turns better. The maximum brightness is 25285 cd/m². The maximum current efficiency is 65.9 cd/A. And the maximum EQE is 17.3%. The method of adding ionic compounds to the perovskite precursor can not only improve the carrier transport behavior, but also make the formed small n crystal phases and large n crystal phase more balance, leading to the energy funnel effect to be enhanced. Further investigation by FTIR proves that the TPPCl can passivate the perovskite film, and thus greatly improving the EQE value of the PeLED. This researchpresents a simple and efficient method of developing high-performance quasi-two-dimensional green PeLEDs.