84% efficiency improvement in all-inorganic perovskite light-emitting diodes assisted by a phosphorescent material.

A novel mixed perovskite emitter layer is applied to design all-inorganic cesium lead halide perovskite light-emitting diodes (PeLEDs) with high electroluminescence (EL) performance, by combining CsPbBr 3 with iridium(iii)bis[2-(4',6'-difluorophenyl)pyridinato-N,C 2 ']-picolinate (FIrpic), where FIrpic is a phosphorescent material with very high internal quantum efficiency (IQE) approaching 100%. The CsPbBr 3 :FIrpic PeLEDs show a maximum luminance of 5486 cd m -2 , and an external quantum efficiency of 0.47%, which are 1.84 and 1.76 times that of neat CsPbBr 3 PeLEDs, respectively. It is found that FIrpic molecules as an assistant dopant can efficiently transmit energy from the excitons of FIrpic to the excited state of the CsPbBr 3 emitter via a Förster energy transfer process, leading to enhanced EL efficiency in the CsPbBr 3 :FIrpic PeLEDs.