Realizing Efficient Single Organic Molecular White Light-Emitting Diodes from Conformational Isomerization of Quinazoline-Based Emitter.

Single pure organic molecular white light emitters (SPOMWLEs) are of significance as a new class material for white lighting applications, and however, few of them are able to emit white electroluminescence from organic light-emitting diodes. Herein, donor-π-acceptor conjugated emitters, 2PQ-PTZ and 4PQ-PTZ, were designed and synthesized as SPOMWLEs for white light emission by taking the distinct advantages of their conformation isomers. The co-existence of conformational isomers in 2PQ-PTZ, which is the first experimental evidence of the co-existed quasi-axial and quasi-equatorial conformers, provides an ideal flexibility to obtain white light emission from their simultaneous and well-separated fluorescence and thermally activated delayed fluorescence. With this remarkable properties, 2PQ-PTZ-based white light-emitting diode (LED) with CIE of (0.32, 0.34) and color-rendering index (CRI) of 89 is demonstrated. Further, white organic light-emitting diode (OLED) of 2PQ-PTZ exhibits a high external quantum efficiency (EQE) of 10.1%, which is the reported highest performance among SPOMWLEs-based OLEDs.