Achieving Dual Persistent Room-Temperature Phosphorescence from Polycyclic Luminophores via Inter-/Intramolecular Charge Transfer

Organic persistent room-temperature phosphorescence (OPRTP) materials show great prospects in optoelectronic and biomedical applications, such as display, anti-counterfeiting, sensing, and bioimaging. However, the reported OPRTP material systems are relatively rare, and it is a challenge to achieve the tunability of OPRTP. In this work, a series of polycyclic luminophores are developed based on an indole derivative (6,12-diphenyl-5,6,11,12-tetrahydroindolo[3,2-b] carbazole, Ben-H) as the structural skeleton. These compounds unexpectedly exhibit dual OPRTP at 442 to 623 nm with lifetimes spanning from 2 to 759 ms. Experimental data and theoretical calculations suggest that C-H...pi interactions in the T-shaped dimers facilitate the intermolecular charge transfer, resulting in OPRTP in the yellow spectral region, and the persistent blue emission results from the intramolecular charge transfer. This work contributes to better understand the key role of charge transfer in achieving OPRTP and broaden the scope of OPRTP materials.