Zhu Yuanyuan, Zeng Songkun, Li Bing, McEllin Alice J, Liao Junxu, Fang Zhou, Xiao Chen, Bruce Duncan W, Zhu Weiguo, Wang Yafei
School of Materials Science & Engineering, Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering, Jiangsu Engineering Laboratory of Light-Electricity-Heat Energy-Converting Materials and Applications, Changzhou University, Changzhou 213164, PR China.
Department of Chemistry, University of York, Heslington, York YO10 5DD, United Kingdom.
ACS Appl Mater Interfaces. 2022 Apr 6;14(13):15437-15447. doi: 10.1021/acsami.1c19932. Epub 2022 Mar 24.
Realizing both high efficiency and liquid crystallinity in one molecule remains a challenge in thermally activated delayed fluorescence (TADF) emission. Herein, two isomeric compounds─-DPSAc-LC and -DPSAc-LC with different connection positions between donor and acceptor moieties─were synthesized and characterized. Diphenylsulfone (DPS) was used as the acceptor, acridine (Ac) was used as the donor, and biphenyl derivatives (LC) were employed as the mesogenic group. Both compounds showed a smectic mesophase evidenced by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and temperature-dependent small-angle X-ray scattering (SAXS). The compound -DPSAc-LC clearly exhibited thermally activated delayed fluorescence due to the much more distorted geometry, whereas -DPSAc-LC showed simple fluorescence. Compared to the parent TADF molecules without appended mesogenic groups (DPS-Ac), these liquid-crystalline emitters possessed higher hole mobilities and improved device performance. The OLEDs fabricated via solution processing using the liquid-crystalline compound -DPSAc showed a maximum external quantum efficiency of ∼15% and as such is the first example of a liquid-crystalline TADF material in an OLED device.
在热激活延迟荧光（TADF）发射中，在一个分子中同时实现高效率和液晶性仍然是一个挑战。在此，合成并表征了两种异构体化合物——供体和受体部分之间连接位置不同的-DPSAc-LC和-DPSAc-LC。二苯砜（DPS）用作受体，吖啶（Ac）用作供体，联苯衍生物（LC）用作介晶基团。差示扫描量热法（DSC）、偏光显微镜（POM）和变温小角X射线散射（SAXS）表明这两种化合物均呈现近晶相。由于几何结构扭曲得多，化合物-DPSAc-LC明显表现出热激活延迟荧光，而-DPSAc-LC表现出简单荧光。与未连接介晶基团的母体TADF分子（DPS-Ac）相比，这些液晶发射体具有更高的空穴迁移率和更好的器件性能。使用液晶化合物-DPSAc通过溶液处理制备的OLED的最大外量子效率约为15%，因此是OLED器件中液晶TADF材料的首个实例。
