Adv. Funct. Mater.: Enhancing Reverse Intersystem Crossing of Multiple Resonance Type Thermally Activated Delayed Fluorescence Emitter by Introducing Spatial Perturbation

Title：

Enhancing Reverse Intersystem Crossing of Multiple Resonance Type Thermally Activated Delayed Fluorescence Emitter by Introducing Spatial Perturbation

Authors：

Xin Xiong¹, Jia-Qi Li¹, Ting-Feng Chen¹, Xiao-Chun Fan¹, Ying-Chun Cheng¹, Hui Wang¹, Feng Huang¹, Hao Wu¹, Jia Yu¹, Xian-Kai Chen^1,2*, Kai Wang^1,3* and Xiao-Hong Zhang^1,2*

Institutions：

¹Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, 199 Ren-Ai Road, Suzhou 215123, China

²Jiangsu Key Laboratory of Advanced Negative Carbon Technologies Soochow University Suzhou, Jiangsu 215123, P. R. China

³Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices Soochow University Suzhou, Jiangsu 215123, P. R. China

Abstract：

For multiple resonance (MR) type thermally activated delayed fluorescence (TADF) emitters, electron cloud distributions of their π-conjugated planes are crucial for determining their eventual performance. Currently, modulation attempts of MR-TADF emitters are mainly inside the π-conjugated planes. Possible out-of-plane interactions may also significantly impact the photophysical properties, but the exploration is quite limited. Here, a novel concept of using out-of-plane (e.g., π–π and lone pair-π) interactions to introduce spatial perturbation (SPPT) to improve TADF performance is proposed. Two newly developed MR-TADF emitters, namely,o-BNPOandBNPO, which both consist of a popular MR framework,DtBuCzB, and diphenylphosphine oxide (DPPO), are compared in depth. In particular, foro-BNPO, evident π–π interaction is observed between one side of theDtBuCzBπ-conjugated plane and a phenyl ring fromDPPO, and lone pair-π interaction with the oxygen atom fromDPPOis noticed on the other side, resulting in significantly accelerated reverse intersystem crossing and better TADF without sacrificing narrowband emission features. Ultimately, in organic light-emitting diodes with sensitizer-free emitting layers, both emitters achieve similar narrowband emissions, while theo-BNPO-based device demonstrates a much higher external quantum efficiency of 36% and milder efficiency roll-off.

IF：

19.924

Link：

https://onlinelibrary.wiley.com/doi/full/10.1002/adfm.202313726