Dual fluorescence induced thermally activated delayed fluorescence materials based on 2,4-Diphenylthieno[3,2-d]pyrimidine with an efficient single-molecular white electroluminescence

Dual fluorescence compounds exhibit a wide emission spectrum in visible-light range and show huge application prospect in white-light OLED (WOLED). However, few of them can realize the trade-off between high color purity of white-light emission and high emission efficiency. In this work, using sulfur atom-fused electron acceptor (A) unit 2,4-diphenylthieno[3,2-d]pyrimidine (TP) and planar electron donor (D) unit phenothiazine (PTZ), a series of novel dual fluorescence compounds with simple twisting D-A configuration were designed and synthesized, denoted as PTZ-2TP, PTZ-4TP and DPTZ-TP, respectively. Simultaneous dual fluorescence emission could be realized both solution and film state of the current system via optimizing polarization environment and doped concentration, which are attributed to the characteristic quasi-axial (QA) and quasi-equal (QE) conformations. Subsequently, these compounds were successfully applied in WOLED with high efficiency. DPTZ-TP as emitter endows the WOLED with the best device performance with greenish-white light emission, CIE coordinates of (0.33, 0.44) and high EQEmax of 11.87%, which is the highest records of such single compound systems.