Abstract
Three novel small organic heterocyclic compounds: 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 possible applications as blue OLED emitters. The specific molecular design targeted decreasing intermolecular aggregation and disrupting crystallinity in the solid-state, in order to reduce dye aggregation, and thus obtain efficient pure blue photo- and electroluminescence. Accordingly, the new compounds displayed reasonably high spectral purity in both solution- and solid-states with average CIE coordinates of (0.160 ± 0.005, 0.029 ± 0.009) in solution and (0.152 ± 0.007, 0.126 ± 0.005) in solid-state. These compounds showed a systematic decrease in degree of crystallinity and intermolecular aggregation due to increasing steric hindrance, as revealed using powder X-ray diffraction analysis and spectroscopic studies. An organic light-emitting diode (OLED) prototype fabricated using compound B as the non-doped emissive layer displayed an external quantum efficiency (EQE) of 0.35 (±0.04)% and luminance 100 (±6) cd m−2 at 5.5 V with an essentially pure blue electroluminescence corresponding to CIE coordinates of (0.1482, 0.1300). The highest EQE observed from this OLED prototype was 4.3 (±0.3)% at 3.5 V, and the highest luminance of 290 (±10) cd m−2 at 7.5 V. These values were found comparable to characteristics of the best pure blue OLED devices based on simple fluorescent small-molecule organic chromophores.
Funder
National Science Foundation
National Aeronautics and Space Administration
Louisiana Board of Regents
Louisiana State University
Subject
Chemistry (miscellaneous),Analytical Chemistry,Organic Chemistry,Physical and Theoretical Chemistry,Molecular Medicine,Drug Discovery,Pharmaceutical Science
Cited by
11 articles.
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