Manipulating the Trade-off Between Quantum Yield and Electrical Conductivity for High-Brightness Quasi-2D Perovskite Light-Emitting Diodes

Quasi-two-dimensional (quasi-2D) perovskites are attracting much attention due to their impressive luminescence properties. However, the introduction of insulating bulky cations reduces the charge transport property of mixed-dimensional perovskites and leads to lowered brightness and increased turn-on voltage. The trade-off between high photoluminescence quantum yield (PLQY) and electrical conductivity should be well manipulated to obtain high-performance perovskite light-emitting diodes (PeLEDs). Herein, quasi-2D perovskite BA₂(CsPbBr₃)_n-1PbBr₄-PEO with high PLQY and excellent carrier injection efficiency is demonstrated by incorporating bulky n-butylammonium bromide (BABr), CsPbBr₃, and polyethylene oxide (PEO). BA can intercalate into the three-dimensional perovskite framework to form a layered (quasi-2D) perovskite structure. The ion conductive polymer PEO is used to protect quasi-2D perovskite crystals. Additional BABr is removed by using anhydrous isopropyl alcohol as a washing agent due to its selective dissolubility. By carefully modulating the optical and electrical properties of quasi-2D perovskite films, the maximum luminance of PeLEDs is dramatically enhanced from 191 to 33533 cd m⁻², which is the brightest green quasi-2D PeLED reported thus far, leading to an increase in external quantum efficiency from 1.81% to 8.42%. This work provides a promising route to control the optical and electrical properties of quasi-2D perovskite films for high-performance optoelectronic devices.