Solution-processed diarylfluorene derivatives for violet-blue amplified spontaneous emission and electroluminescence

Abstract

A series of solution-processable diarylfluorene-based materials with pendent 4-(hexyloxy carbazole)-9,9-diphenyl-9H-fluorene (MC₆Cz) or 4-(octyloxy)-9,9-diphenyl-9H-fluorene (MC₈) as the core and endcapped with different charge transport moieties such as phenylcarbazole (NPC) or triphenylemine (TPA) have been synthesized and investigated systemically. These materials exhibited bright fluorescence emission from violet-blue to deep blue without molecular aggregation in diluted solutions and films. Furthermore, these materials also displayed prominent virtues including superior solution-processability and amorphous characteristics. Consequently, the EL spectra of the solution-processed organic light-emitting diodes (OLEDs) are expected to be similar to the corresponding PL spectra, suggesting intramolecular photophysical behavior. MC₆Cz-9-NPC as an emitting layer presented the highest maximum luminance of about 1560 cd m⁻² with a lower turn on voltage of 3.5 V. In contrast, the ASE results revealed that the MC₈ core-containing compounds exhibited relatively lower thresholds comparable with traditional conjugated or star type polymers, which could be promising optical gain media. We proposed a novel molecular design strategy to construct high-performance solution-processed violet-blue fluorophores.