Highly efficient non-doped blue organic light emitting diodes based on a D–π–A chromophore with different donor moieties

Abstract

Comparative photophysical, electroluminance and theoretical investigations have been made for 4′-(1-(4-morpholinophenyl)-1H-phenanthro[9,10-d]imidazole-2-yl)-styryl-2-(4′-9H-carbazole-9-yl) (MPPIS-Cz) and 4′-(1-(4-morpholinophenyl)-1H-phenanthro[9,10-d]imidazole-2-yl)-styryl-N,N-diphenyl-[1,1′-biphenyl]-4-amine (MPPIS-TPA). Based on tuning the donor ability, MPPIS-TPA and MPPIS-Cz were designed to have a hybridized local and charge transfer state (HLCT) and a hot exciton channel. This HLCT is responsible for high photoluminescence efficiency and the hot exciton contributes to high exciton utilization. The non-doped OLED based on MPPIS-Cz exhibits excellent performance: blue emission with CIE coordinates of (0.16, 0.08), maximum current efficiency of 1.52 cd A⁻¹ and maximum external quantum efficiency of 1.42%. A fluorescent molecule with a HLCT state and hot exciton may be an ideal strategy to design next generation, high efficiency and low cost fluorescent OLED materials.