Combined optimization of emission layer morphology and hole-transport layer for enhanced performance of perovskite light-emitting diodes

Electroluminescence performance of perovskite light-emitting diodes (PeLEDs) is extremely dependent on the morphology of the perovskite films, which is influenced by the processing method. Herein, we report an effective approach for the preparation of a high-quality perovskite film with perfect performance for PeLEDs via a solution process at room temperature. On the one hand, CH₃NH₃PbBr₃ (MAPbBr₃) precursor solution was blended with a traditional polymeric host PVK [poly(vinylcarbazole)] to obtain smooth and uniform perovskite films. On the other hand, the perovskite films could be further improved through crystal modification to obtain a more uniform morphology and smaller grain sizes. Our research also demonstrated the feasibility of preparing high-performance solution-processed PeLEDs by blending small molecule hole-transport materials (HTMs) with polymer HTMs (widely used in OLEDs as hole-transport layers (HTLs)). Efficient green PeLEDs with a current efficiency (CE) of 6.7 cd A^-1, external quantum efficiency (EQE) of 1.88%, and low turn-on voltage of 2.9 V were achieved; this indicates that the effective solution process used to improve the morphology of the perovskite films as well as carrier injection has great potential for the development of high-performance PeLEDs.