47-Fold EQE improvement in CsPbBr3 perovskite light-emitting diodes via double-additives assistance

Abstract

All-inorganic cesium halide perovskite materials are intensively investigated due to their excellent photoelectric characteristics, but poor film coverage, unbalanced charge carrier transporting and insufficient exciton harvesting are remaining challenges to be overcome in order to achieve high electroluminescent (EL) performance in perovskite light-emitting diodes (PeLEDs). Here we show that these problems can be solved by introducing both a phosphorescent sensitizer (FIrpic) and an electron transporting material (TmPyPB) into all-inorganic cesium halide perovskite (CsPbBr 3 ). And highly efficient green PeLEDs with full coverage CsPbBr 3 :TmPyPB:FIrpic film as the emissive layer have been achieved, exhibiting the maximum luminance of 37784 cd/m 2 , the maximum current efficiency of 22.6 cd/A and the corresponding maximum external quantum efficiency (EQE) of 5.85%, where the EQE is 48-fold to that of bare CsPbBr 3 PeLEDs. The enhanced EL performance is attributed to less non-radiative current leakage, better film surface passivation effect, balanced charge carrier injection and transportation, as well as better exciton harvesting. It is believed that our work will provide an effective strategy to further improve EL performance of PeLEDs via better exciton harvesting. • Excellent enhanced electroluminescent performances were realized in CsPbBr 3 :TmPyPB:FIrpic based PeLEDs. • Pinhole-free and continuous CsPbBr 3 :TmPyPB:FIrpic perovskite films was achieved. • The current leakage was largely reduced. • More balanced charge carrier transporting behavior in perovskite emitting layer was reached. • Improved exciton harvesting was realized due to Förster and Dexter energy transfer processes.