Single-Molecule Color-Stable Cool-WOLED Emitters with Multicolored Emission.

Single-molecule white-light emitters have attracted much attention due to their potential applications in white organic light-emitting diodes (WOLEDs). Their key advantage lies in the ability to use a simple device structure, akin to that of monochromatic OLEDs, to produce WOLEDs. This approach not only simplifies the fabrication process but also reduces costs, improves device stability, and provides a shortcut for the rapid commercialization of WOLEDs. In this study, two novel single-molecule white-light emitters, SRFR-1PTZ (10-(4'-(9H-9,9'-spirobi[fluoren]-2-yl)-4a,10a-dihydro-10H-phenothiazine) and SRFR-2PTZ (2,7-bis(4a,10a-dihydro-10H-phenothiazin-10-yl)-9,9'-spirobi[fluorene]), were designed and synthesized, and successfully implemented in WOLED devices. Comprehensive photophysical characterization revealed that both compounds exhibited dual-emission characteristics in dichloromethane solution, displaying simultaneous fluorescence and phosphorescence. Notably, thermally activated delayed fluorescence (TADF) was clearly observed for SRFR-1PTZ, whereas SRFR-2PTZ did not exhibit TADF behavior. Electroluminescence studies demonstrated that both SRFR-1PTZ and SRFR-2PTZ served as good color-stable cool-white-light emitters under driving voltages of 7-10 V.