Anthracene-bridged D–π–A fluorescent molecule featuring multiple channels for triplet exciton harvesting

Recent research has garnered significant attention for exploring highly efficient organic light-emitting diode (OLED) devices that utilize excitons generated in the triplet excited state. In this study, AML23–1 and AML23–2 were successfully synthesized by altering the number of fluorene units used as electron donors in the anthracene-phenanthroimidazole derivative. Detailed photophysical investigations, along with DFT analysis, suggest hybridized local and charge transfer (HLCT) characteristics for both materials. The incorporation of D-π-A pairs promoted a unique electronic distribution, effectively narrowing the energy gap between the S₁ and T_n (n = 2 or 3) states. Additionally, the stable T₁ level of anthracene facilitated the transition to triplet-triplet fusion (TTF), enabling the recycling of dark triplet excitons. Finally, five non-doped devices using AML23–1 were fabricated with varying charge balances. The optimized device exhibited a maximum external quantum efficiency (EQE) of 4.84 % with low efficiency roll-off and Commission Internationale de l’Éclairage (CIE) coordinates of (0.157, 0.296).