Efficient rare earth cerium(III) complex with nanosecond d-f emission for blue organic light-emitting diodes
Abstract Blue organic light-emitting diode (OLED) is still a challenge among the RGB ones due to the lack of emitter simultaneously has short excited state lifetime and high theoretical external quantum efficiency (EQE). We demonstrate herein a blue emissive rare earth cerium(III) complex Ce-2 showing a high photoluminescence quantum yield of 95% and a short excited state lifetime of 52.0 ns in doped film, which is considerably faster than that achieved in typical efficient phosphorescence or thermally activated delayed fluorescence emitters (typical lifetimes > 1 μs). The corresponding OLED shows a maximum EQE up to 20.8% and a still high EQE of 18.2% at 1000 cd m−2, as well as a 70 times longer operation lifetime than a classic phosphorescence OLED. The excellent performance indicates that cerium(III) complex could be a candidate for efficient and stable blue OLEDs because of its spin- and parity-allowed d-f transition from Ce3+ ion.
