Design and synthesis of novel anthracene derivatives as n-type emitters for electroluminescent devices: a combined experimental and DFT study
作者:G. Mallesham、S. Balaiah、M. Ananth Reddy、B. Sridhar、Punita Singh、Ritu Srivastava、K. Bhanuprakash、V. Jayathirtha Rao
DOI:10.1039/c3pp50284h
日期:2014.2
Six novel anthracene-oxadiazole derivatives, 4a (2-(4-(anthracen-9-yl)phenyl)-5- p-tolyl-1,3,4-oxadiazole), 4b (2-(4-(anthracen-9-yl)phenyl)-5-(4- tert-butylphenyl)-1,3,4-oxadiazole), 4c (2-(4-(anthracen-9-yl)phenyl)-5-(4-methoxyphenyl)-1,3,4-oxadiazole), 8a (2-(4-(anthracen-9-yl)phenyl)-5- m-tolyl-1,3,4-oxadiazole), 8b (2-(3-(anthracen-9-yl)phenyl)-5-(4- tert-butylphenyl)-1,3,4-oxadiazole) and 8c (2-(3-(anthracen-9-yl)phenyl)-5-(3,4,5-trimethoxyphenyl)-1,3,4-oxadiazole) have been synthesized and characterized for use as emitters in organic light emitting devices (OLEDs). They show good thermal stability (Td, 297–364 °C) and glass transition temperatures (Tg) in the range of 82–98 °C, as seen from the thermo gravimetric analysis and differential scanning calorimetric studies. The solvatochromism phenomenon and electrochemical properties have been studied in detail using UV-Vis absorption, fluorescence spectroscopy and cyclic voltammetry. TD-DFT calculations have been carried out to understand the electrochemical and photophysical properties. The spatial structures of 4b and 8c are further confirmed by X-ray diffraction analysis. Un-optimized non-doped electroluminescent devices were fabricated using these anthracene derivatives as emitters with the following device configuration: ITO (120 nm)/α-NPD (30 nm)/ 4a–4c or 8a–8c (35 nm)/BCP (6 nm)/Alq3 (28 nm)/LiF (1 nm)/Al (150 nm). Among all the six compounds, 8a displays the maximum brightness of 1728 cd m−2 and current efficiency 0.89 cd A−1. Furthermore, as an electron transporter, 8a exhibited superior performance (current efficiency is 11.7 cd A−1) than the device using standard Alq3 (current efficiency is 8.69 cd A−1), demonstrating its high potential for employment in OLEDs. These results indicate that the new anthracene-oxadiazole derivatives could play an important role in the development of OLEDs.
合成并表征了六种新型蒽-噁二唑衍生物,分别为:4a(2-(4-(蒽-9-基)苯基)-5-p-甲基苯基-1,3,4-噁二唑)、4b(2-(4-(蒽-9-基)苯基)-5-(4-叔丁基苯基)-1,3,4-噁二唑)、4c(2-(4-(蒽-9-基)苯基)-5-(4-甲氧基苯基)-1,3,4-噁二唑)、8a(2-(4-(蒽-9-基)苯基)-5-m-甲基苯基-1,3,4-噁二唑)、8b(2-(3-(蒽-9-基)苯基)-5-(4-叔丁基苯基)-1,3,4-噁二唑)和8c(2-(3-(蒽-9-基)苯基)-5-(3,4,5-三甲氧基苯基)-1,3,4-噁二唑),用于有机发光器件(OLEDs)中的发光材料。通过热重分析和差示扫描量热研究显示,它们具有良好的热稳定性(Td,297–364 °C)和玻璃转变温度(Tg),范围为82–98 °C。使用紫外-可见吸收、荧光光谱和循环伏安法对溶剂色变现象和电化学性质进行了详细研究。开展了TD-DFT计算以理解其电化学和光物理性质。通过X射线衍射分析进一步确认了4b和8c的空间结构。采用这些蒽衍生物作为发光材料制备了未优化的非掺杂电致发光器件,器件配置为:ITO(120 nm)/α-NPD(30 nm)/4a–4c或8a–8c(35 nm)/BCP(6 nm)/Alq3(28 nm)/LiF(1 nm)/Al(150 nm)。在这六种化合物中,8a表现出最高亮度1728 cd m−2和电流效率0.89 cd A−1。此外,作为电子传输材料,8a的性能优于采用标准Alq3的器件(电流效率为8.69 cd A−1),显示出其在OLEDs中的应用潜力。这些结果表明,新型蒽-噁二唑衍生物在OLEDs的发展中可能发挥重要作用。