1,8-diphenyl-carbazole-based boron, sulfur-containing multi-resonance emitters with suppressed aggregation emission for narrowband OLEDs.

Multi-resonance emitters are attractive for organic light-emitting diode (OLED) applications because of their narrowband emissions and high photoluminescent efficiencies. Nevertheless, their tendency to aggregation by intermolecular interactions could cause doping sensitivity and reduce color purity at high concentrations. Here, we report a novel boron, sulfur (B, S)-containing multi-resonance emitter (BSS-Ph-TBCz) consisting of 1,8-diphenyl-carbazole substituent at para- position of boron atom of B, S-doped polycyclic aromatic skeleton. Different from control compound (BSS-TBCz) containing conventional carbazole substituents showing aggregation-caused spectral broadening, BSS-Ph-TBCz with 1,8-diphenyl-carbazole group exhibits weak intermolecular aggregation behavior owing to the large twist angle between polycyclic skeleton and carbazole plane caused by two steric phenyl groups on carbazole group, leading to nearly unchanged emissions with small full width at half-maximum of 30–31 nm at doping concentration ranging from 1 to 100 wt%. OLEDs employing BSS-Ph-TBCz as emitter reveal blue electroluminescence at 468 nm and maximum external quantum efficiency of 21.4% at 5 wt% doping concentration, which remains at 20.1% at high doping concentration of 25 wt%. [Display omitted] • Novel multi-resonance emitter with 1,8-diphenyl-carbazole substituent is developed. • Aggregation emission is suppressed by steric hindrance of 1,8-diphenyl-carbazole. • Rapid reverse intersystem crossing is realized by heavy-atom effect of sulfur. • EQE of >20% and FWHM of 31 nm are achieved for OLEDs at high doping concentration. [ABSTRACT FROM AUTHOR]