Efficient red phosphorescent organic light emitting diodes based on solution processed all-inorganic cesium lead halide perovskite as hole transporting layer

Abstract An efficient red phosphorescent organic light emitting diode (PhOLED) has been realized by utilizing a composite hole transporting layer comprised of all-inorganic cesium lead halide perovskite CsPbBr 3 via spin-coating and 1,3-bis(9-carbazolyl) benzene (mCP) by vacuum depositing, in which CsPbBr 3 film is used as a hole transporting layer and mCP plays a dominant role in electron and exciton blocking. And this PhOLED shows a saturated red emission coordinated at CIE (0.65, 0.33) driven at 7.5 V, a maximum brightness of 20,750 cd/m 2 , and a maximum current efficiency of 10.64 cd/A, which is as 1.87 times as that 5.68 cd/A of the reference PhOLEDs based on traditional small organic molecular hole transporting material N , N ′-bis(naphthalen-1-yl)- N , N ′-bis(phenyl)-benzi (NPB). The electroluminescent (EL) spectra and the energy level alignment of different PhOLEDs are investigated. The enhanced EL performances are ascribed to improved hole injecting and transporting behaviors, and better electron and exciton confinements by introducing the composite hole transporting layer CsPbBr 3 /mCP.