Asymmetric steric-hindrance donor engineering enables ACQ-suppressed MR-TADF emitters for high-efficiency narrowband OLEDs

Abstract

A new organic emitter, mPhCz-QAO, was designed and synthesized through an asymmetric steric-hindrance donor strategy, establishing a distinctive molecular-engineering approach for achieving both high efficiency and narrowband emission in organic light-emitting materials. By introducing a meta-position asymmetric bulky donor, the strong intermolecular π-π interactions intrinsic to the QAO framework are effectively suppressed, thereby preventing aggregation-caused quenching (ACQ) in the solid state. This asymmetric donor simultaneously promotes a more delocalized distribution of the frontier molecular orbitals and strengthens the radiative transition process, leading to enhanced emission properties. Devices incorporating mPhCz-QAO exhibit exceptionally good performance at elevated doping levels, maintaining a maximum external quantum efficiency of approximately 22% as the doping concentration increases from 3 wt.% to 10 wt.%. The emission peak displays only a minimal shift (from 486 to 488 nm), while the narrow emission bandwidth of 38 nm remains fully preserved. These findings demonstrate the effectiveness of asymmetric donor engineering in overcoming concentration-related emission quenching and provide a powerful design framework for developing next-generation high-efficiency, high-color-purity organic emitters suitable for advanced display and lighting technologies.

Keywords

Asymmetric / Steric hindrance donor / Multi-resonance / Thermally activated delayed fluorescence / QAO / Organic light-emitting diodes

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

CRediT authorship contribution statement

Chengxiang Shi: Writing – review & editing, Writing – original draft, Methodology, Investigation, Formal analysis. Ya-Rong Gong: Writing – original draft, Validation, Investigation, Formal analysis. Jia-Ming Jin: Methodology, Investigation, Formal analysis. Yan Li: Formal analysis. Li-Ting Zhong: Data curation. Xiao-Long Liu: Formal analysis. Jun-Hua Zhuang: Investigation. Shao-Liang Shan: Formal analysis. Xuechen Jiao: Investigation, Funding acquisition. Ji-Hua Tan: Writing – review & editing, Supervision, Methodology, Investigation, Formal analysis. Yanping Huo: Writing – review & editing, Supervision, Project administration, Funding acquisition. Ze-Lin Zhu: Writing – review & editing, Supervision, Investigation. Wen-Cheng Chen: Writing – review & editing, Writing – original draft, Supervision, Project administration, Funding acquisition, Formal analysis, Conceptualization.

Acknowledgements

We gratefully acknowledge financial support from the National Natural Science Foundation of China (Grant Nos. U22A20399 and U23A20594), the Guangdong Provincial Laboratory of Chemistry and Fine Chemical Engineering Jieyang Center (Grant No. RJDT240026), Anhui Provincial Natural Science Foundation (Grant No. 2308085MA19), National Excellent Engineers Innovation Institute of Guangdong-Hong Kong-Macao Greater Bay Area (Foshan) Advanced Manufacturing Industry (Grant No. JBGS2024007). The authors also thank the Instrumental Analysis Center of Guangdong University of Technology for assistance with mass spectrometry, thermogravimetric analysis, and differential scanning calorimetry measurements.

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