Multi‐Layer π‐Stacked Molecules as Efficient Thermally Activated Delayed Fluorescence Emitters

• Published in: Angewandte Chemie International Edition Vol. 60; no. 10; pp. 5213 - 5219
• Main Authors: Wang, Xue‐Qi, Yang, Sheng‐Yi, Tian, Qi‐Sheng, Zhong, Cheng, Qu, Yang‐Kun, Yu, You‐Jun, Jiang, Zuo‐Quan, Liao, Liang‐Sheng
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.03.2021
• Edition: International ed. in English
• Subjects: Charge transfer; donor/acceptor interactions; Emitters; Fluorescence; Photoluminescence; Photons; spiro structures; thermally activated delayed fluorescence; π-stacked molecules; thermally activated delayed fluorescence; donor/acceptor interactions; spiro structures; π-stacked molecules; charge transfer
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202011384

Multi‐layer π‐stacked emitters based on spatially confined donor/acceptor/donor (D/A/D) patterns have been developed to achieve high‐efficiency thermally activated delayed fluorescence (TADF). In this case, dual donor moieties and a single acceptor moiety are introduced to form two three‐dimensional (3D) emitters, DM‐BD1 and DM‐BD2, which rely on spatial charge transfer (CT). Owing to the enforced face‐to‐face D/A/D pattern, effective CT interactions are realized, which lead to high photoluminescence quantum yields (PLQYs) of 94.2 % and 92.8 % for the two molecules, respectively. The resulting emitters exhibit small singlet–triplet energy splitting (ΔEST) and fast reverse intersystem crossing (RISC) processes. Maximum external quantum efficiencies (EQEs) of 28.0 % and 26.6 % were realized for devices based on DM‐BD1 and DM‐BD2, respectively, which are higher than those of their D/A‐type analogues. Multi‐Layer π‐stacked molecules are designed to realize efficient thermally activated delayed fluorescence. Spatially confined molecules with stereochemical structures are constructed in donor/acceptor/donor architectures with different conformations. Their organic light‐emitting diode (OLED) devices exhibit high external quantum efficiencies (EQEs) of 28.0 %/26.6 %, respectively.