A series of thermally activated delayed fluorescence (TADF) emitters with folded-layout, namely SF12oTz, SF23oTz and SF34oTz are strategically designed and synthesized by substituting 4,6-diphenyl-1,3,5-triazine (Tz) with indoline-fused spirobifluorene donors at the ortho position. The substitution position of the spirobifluorene-based donors changes the steric hindrance and conjugation degree of molecules, which dominate the excited state levels (singlet and triplet) and intramolecular charge transfer (ICT) state properties, resulting in simultaneous through bond charge transfer (TBCT) and through space charge transfer (TSCT) transitions in one single molecule. Among them, SF23oTz and SF12oTz both show dual emissions with LE (local excited) and CT (charge transfer) features in different solvents, whereas SF34oTz possesses single emission from TSCT (96.8%) contributed S₁. Furthermore, SF12oTz exhibits more TBCT (32.0%) contributed emission compared with SF23oTz (20.6%), which results in much higher ratio of delayed fluorescence (79.1% vs. 39.2%) because of the more effective channel of TBCT over TSCT to realize charge transfer from donors to acceptor. In devices, SF12oTz and SF23oTz with more contribution of TBCT achieve high EQE_max of 22.4% and 19.6% with reduced efficiency roll-off. The mechanism studies reveal that the control of TBCT and TSCT in these molecules play a significant role in regulating photophysical properties and improving the device performance of TADF-OLEDs.

通过将4,6-二苯基-1,3,5-三嗪（Tz）替换为二氢吲哚稠合的螺二芴，策略性地设计和合成了一系列具有折叠布局的热激活延迟荧光（TADF）发射器，即SF12oTz，SF23oTz和SF34oTz。邻位供体。螺二芴基供体的取代位置改变了分子的位阻和共轭度，支配了激发态能级（单重态和三重态）和分子内电荷转移（ICT）的状态特性，从而导致通过键合电荷转移（TBCT）的同时发生并通过一个分子中的空间电荷转移（TSCT）跃迁。其中，SF23oTz和SF12oTz两者均显示出在不同溶剂中具有LE（局部激发）和CT（电荷转移）特征的双重发射，而SF34oTz具有TSCT的单一发射（96.8％）贡献了S ₁。此外，与SF23oTz（20.6％）相比，SF12oTz表现出更多的TBCT（32.0％）贡献发射，这导致延迟荧光的比率更高（79.1％对39.2％），因为TBCT比TSCT更有效的通道来实现电荷从捐赠者转移到接受者。在设备，SF12oTz和SF23oTz与TBCT的更大的贡献达到高EQE_最高分别降低了22.4％和19.6％，降低了效率下降。机理研究表明，这些分子中TBCT和TSCT的控制在调节光物理性质和改善TADF-OLED的器件性能方面起着重要作用。