Three novel organic blue emitters: 2-(1,2-diphenyl)-1H-benzimidazole-7-tert-butylpyrene (compound A), 1,3-di(1,2-diphenyl)-1H-benzimidazole-7-tert-butylpyrene (compound B), and 1,3,6,8-tetra(1,2-diphenyl)-1H-benzimidazolepyrene (compound C) were synthesized and characterized for application as blue OLED emitters. These compounds displayed reasonably high spectral purity in the solid-state as compared to many pyrene derivatives reported in the literature. As a result of reduced π-stacking in the solid-state, CIE coordinates were in the range of (0.18±0.2, 0.15±0.1). As expected, compounds A, B, and C showed systematic decrease in the degree of crystallinity as revealed by powder X-ray diffraction analysis. Spectroscopic characteristics such as absorption, photoluminescence, and quantum yields as well as cyclic voltammetry and UV-visible absorption based HOMO–LUMO energies of these materials were found suitable for optoelectronic applications. An organic light-emitting diode (OLED) prototype fabricated using compound B as the emissive layer displayed an external quantum efficiency of 4.3±0.4 % at 3.5 V with a significantly pure blue electroluminescence (CIE coordinates: 0.16, 0.13).

Pyrene-benzimidazole hybrids as novel blue emitters for organic light emitting diodes (OLEDs)

2019 Spring National Meeting

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