Trifluoromethyl enable high-performance single-emitter white organic light-emitting devices based on quinazoline acceptor

Abstract

Single-emitter white organic light-emitting diode (WOLED) based on small organic molecule exhibits great potential in simplifying fabrication process of WOLEDs. However, the design and synthesis of molecule for highly efficient single-emitter WOLED still remains a challenge. Herein, two asymmetric donor-acceptor-acceptor’ (D-A-A’) type molecule (PTZ-PQ-F and PTZ-PQ-CF3) are developed by employing trifluoromethyl (CF3) or fluorine atom as secondary acceptor, which can exhibit white lighting with dual emission bands consisting of blue traditional fluorescence from quasi-axial (ax) conformer and orange thermally activated delayed fluorescence (TADF) from quasi-equatorial (eq) conformer. The introduction of CF3 into PTZ-PQ-CF3 greatly enhanced the photoluminescence quantum yield (PLQY) by suppressing the nonradiative deactivation. Owing to electron-inductive-effect of CF3, the “eq” conformer of PTZ-PQ-CF3 exhibits a much smaller ΔEST of 0.01 eV to realize more efficient reverse intersystem crossing (RISC) process, and then enhance the exciton utilization (nearly 100%) of the whole dual emission system. Consequently, single-emitter WOLEDs based on PTZ-PQ-CF3 show nearly standard white emission with EQE of 13.0% and CIE of (0.35, 0.36) in mCP host and show warm white emission with high EQE of 25.5% and CIE of (0.40, 0.47) in 35 DczPPy host, which are the best performance among reported single-emitter WOLEDs.