Pyrene[4,5-d]imidazole-based Derivatives with Hybridized Local and Charge Transfer State for Highly Efficient Blue and White Organic Light-emitting Diodes with Low Efficiency Roll-off

摘要： A family of pyrene[4,5-d]imidazole derivatives, PyPA, PyPPA, PyPPAC and PyPAC, with different excited state are successfully developed. Among them, PyPPA and PyPPAC possess hybridized local and charge transfer (HLCT) state endowing them with pure blue fluorescence as well as high quantum yields. The nondoped organic light-emitting diode (OLED) based on PyPPA displays Commission Internationale de L’Eclairage coordinates of (0.14, 0.13) and achieves a maximum external quantum efficiency (EQE) of 8.47%, which are among the highest value reported to date for nondoped blue HLCT OLEDs. The nondoped OLED based on PyPPAC exhibits a maximum luminance of 50046 cd m-2 locating in blue region with CIE coordinates of (0.15, 0.21) and harvests the EQE of 6.74% even when the luminance reached over 10000 cd m?2. In addition, they both reveal ultimate exciton utilizing efficiencies of nearly 100%. The potential of blue emitter of PyPPA with HLCT character for application in white OLED (WOLED) is further tested. The efficient two-color hybrid warm WOLED is successfully achieved, which provides the total EQE, power efficiency and current efficiency of up to 21.19%, 61.46 lm W?1 and 62.13 cd A?1, respectively. The nondoped blue OLEDs and hybrid WOLEDs present good color stabilities with low efficiency roll-offs. Our results prove that taking advantage of the HLCT state, nondoped blue OLEDs as well as hybrid WOLEDs with high performance could be realized, which have a promising prospect for the displays and lightings in the future.