Development of Phenanthroimidazole-Based Thermally Activated Delayed Fluorescent Compounds for OLED and Photocatalytic Applications

Abstract

Twelve potent phenanthroimidazole-based thermally activated delayed fluorescent (TADF) emitters were designed using computational calculations. Two nuclear positions, such as N1 and C2 in phenanthroimidazole were substituted with electron acceptor units such as cyanopyridines, cyanobenzenes, benzophenone, benzothiadiazole, and benzoxazole. The theoretical results showed that the substitution of the N1 position with acceptor units yields compounds with low charge injection barriers, balanced charge transport, efficient charge separation, high triplet energy (ET), and low singlet−triplet energy difference (𝛥𝐸𝑆𝑇). Synthesis of selected compounds, SS-1, SS-3, and SS-4 were carried out and their photophysical and thermal properties were evaluated and compared. Theoretical studies revealed that most of the compounds studied exhibited promising properties required for the observation of TADF. All the synthesized compounds exhibited high thermal stability and photophysical analysis of SS-1 disclosed the presence of room temperature phosphorescence (RTP).