Construction of phenanthro[9,10-d]oxazole-based “hot exciton” AIEgens via molecular isomer engineering for efficient blue non-doped OLEDs

Abstract

“Hot exciton” materials with aggregation-induced emission (AIE) properties have tremendous potential for application in high-performance blue non-doped organic light-emitting diodes (OLEDs). In this study, two novel blue fluorophores POT-1 and POT-2 were designed and synthesized by molecular isomer engineering. In two molecules, phenanthro [9,10-d]oxazole/triphenylamine acted as acceptor/donor, and triphenylethylene was used as the AIE-active moieties. Both fluorophores displayed excellent thermal properties and blue emissions with decent fluorescence efficiencies. Theoretical calculations proved that POT-1 and POT-2 possessed hybrid local and charge transfer (HLCT) properties with the “hot exciton” channels from T₃/T₄ to S₁. Additionally, POT-1 and POT-2 also exhibited AIE and mechanochromism effects, especially POT-1 showed a large redshift of 62 nm after grinding. The blue non-doped OLEDs based on the two emitters were prepared and the POT-2-based device demonstrated better performances of 9.48 cd A⁻¹, 8.27 lm W⁻¹ and 4.77 %. These results indicate the feasibility of molecular design via positional isomerization engineering to develop blue AIEgens with HLCT characteristics.