Fine-tuning emission properties of the 9H-phenoselenazine core through substituents engineering for high efficiency purely organic room temperature phosphorescence

The purely organic room temperature phosphorescence (PO-RTP) emitters have gained significant importance because of their wide range of applications in display, biology, security, and many other fields. However, it is critical to address the issue of low photoluminescence quantum yield (PLQY) and lower phosphorescence emission efficiency. In this study, we showed how the abovementioned problems might be resolved to offer superior PO-RTP emission by correctly substituting the main aromatic PO-RTP core. The 10H-phenoselenazine (PSe) core was substituted with heteroaromatic and pure-hydrocarbon substituents to give 10-(4-(tert-butyl)phenyl)-3-dibenzo[b,d]furan-2-yl)-10H-phenoselenazine (PSeDBF) and 10-(4-(tert-butyl)phenyl)-3-(9,9-dimethyl-9H-fluoren-2-yl)-10H-phenoselenazine (PSeFL), respectively. Compared with PSeFL, the PSeDBF displayed higher PLQY, a spin-orbital coupling matrix element 11 times higher, and external quantum efficiency, approximately 45% higher. A high external quantum efficiency of 12.8% combined with PLQY of 59% was achieved in the PSeDBF device, suggesting that proper substituent engineering on the PO-RTP core effectively develops highly efficient PO-RTP devices.