Abstract：
Hole-transporting materials (HTMs) are essential for optoelectronic devices, such as organic light-emitting diodes (OLEDs), dye-sensitized solar cells, and perovskite solar cells. Triarylamines have been employed as HTMs since they were introduced in 1987. However, heteroatoms or side chains embedded in the core skeleton of triarylamines can cause thermal and chemical stability problems. Herein, we report that hexabenzo[a,c,fg,j,l,op]tetracene (HBT), a small nonplanar nanographene, functions as a hydrocarbon HTM with hole transport properties that match those of triarylamine-based HTMs. X-ray structural analysis and theoretical calculations revealed effective multidirectional orbital interactions and transfer integrals for HBT. In-depth experimental and theoretical analyses revealed that the nonplanarity-inducing annulative π-extension can achieve not only a stable amorphous state in bulk films, but also a higher increase in the highest occupied molecular orbital level than conventional linear or cyclic π-extension. Furthermore, an in-house manufactured HBT-based OLED exhibited excellent performance, featuring superior curves for current density-voltage, external quantum efficiency-luminance, and lifetime compared to those of representative triarylamine-based OLEDs. A notable improvement in device lifetime was observed for the HBT-based OLED, highlighting the advantages of the hydrocarbon HTM. This study demonstrates the immense potential of small nonplanar nanographenes for optoelectronic device applications.
摘要：
空穴传输材料(HTMs)是光电器件必不可少的材料,如有机发光二极管(OLED)，染料敏化太阳能电池，和钙钛矿太阳能电池。三芳基胺自1987年引入以来已被用作HTM。然而,杂原子或侧链嵌入在三芳基胺的核心骨架可引起热和化学稳定性问题。在这里，我们报告说，六本苯[a，C,fg,j,l,op]tethracene(HBT)，一个小的非平面纳米石墨烯，作为碳氢化合物HTM，其空穴传输特性与基于三芳基胺的HTM相匹配。X射线结构分析和理论计算揭示了HBT的有效多向轨道相互作用和转移积分。深入的实验和理论分析表明，非平面性诱导的环状π扩展不仅可以在块状薄膜中实现稳定的非晶态，而且，最高占据分子轨道水平的增加也比传统的线性或环状π延伸更高。此外，内部制造的基于HBT的OLED表现出优异的性能，具有优越的电流密度-电压曲线，外量子效率-亮度，和寿命与代表性的基于三芳基胺的OLED相比。对于基于HBT的OLED，观察到器件寿命的显着改善，突出了碳氢化合物HTM的优点。这项研究证明了小型非平面纳米石墨烯在光电器件应用中的巨大潜力。
