De Silva Thenahandi Prasanthi Deepthika, Youm Sang Gil, Fronczek Frank R, Sahasrabudhe Girija, Nesterov Evgueni E, Warner Isiah M
Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA.
Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL 60115, USA.
Molecules. 2021 Oct 28;26(21):6523. doi: 10.3390/molecules26216523.
Three novel small organic heterocyclic compounds: 2-(1,2-diphenyl)-1-benzimidazole-7--butylpyrene (compound ), 1,3-di(1,2-diphenyl)-1-benzimidazole-7--butylpyrene (compound ), and 1,3,6,8-tetra(1,2-diphenyl)-1-benzimidazolepyrene (compound ) 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 as the non-doped emissive layer displayed an external quantum efficiency (EQE) of 0.35 (±0.04)% and luminance 100 (±6) cd m 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 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.
2-(1,2-二苯基)-1-苯并咪唑-7-丁基芘（化合物 ）、1,3-二(1,2-二苯基)-1-苯并咪唑-7-丁基芘（化合物 ）和1,3,6,8-四(1,2-二苯基)-1-苯并咪唑芘（化合物 ），并对其作为蓝色有机发光二极管（OLED）发光材料的潜在应用进行了表征。特定的分子设计旨在减少分子间聚集并破坏固态下的结晶性，以减少染料聚集，从而获得高效的纯蓝光光致发光和电致发光。相应地，这些新化合物在溶液态和固态下均表现出相当高的光谱纯度，溶液态下的平均CIE坐标为(0.160 ± 0.005, 0.029 ± 0.009)，固态下为(0.152 ± 0.007, 0.126 ± 0.005)。粉末X射线衍射分析和光谱研究表明，由于空间位阻增加，这些化合物的结晶度和分子间聚集程度呈系统性降低。以化合物 作为非掺杂发光层制备的有机发光二极管（OLED）原型在5.5 V时的外量子效率（EQE）为0.35 (±0.04)%，亮度为100 (±6) cd m ，发出基本纯蓝色的电致发光，CIE坐标为(0.1482, 0.1300)。该OLED原型在3.5 V时观察到的最高EQE为4.3 (±0.3)%，在7.5 V时的最高亮度为290 (±10) cd m 。发现这些值与基于简单荧光小分子有机发色团的最佳纯蓝色OLED器件的特性相当。
