Affiliation:
1. Zhejiang Provincial Engineering Research Center of Energy Optoelectronic Materials and Devices Ningbo Institute of Materials Technology and Engineering Chinese Academy of Sciences Ningbo 315201 P. R. China
2. Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Beijing 100049 P. R. China
3. State Key Laboratory of Luminescent Materials and Devices and Institute of Polymer Optoelectronic Materials and Devices South China University of Technology Wushan Road 381, Tianhe Guangzhou Guangdong 510640 P. R. China
Abstract
AbstractOvercoming exciton quenching and improving electroluminescence (EL) performances continue to pose persistent challenges in the development of efficient deep blue thermally activated delayed fluorescence (TADF) emitters. Herein, an asymmetric multi‐donors strategy is employed that provides the potential of establishing multiple radiative transition channels for fluorescence emission and reverse intersystem crossing (RISC), while allowing flexible modulation of packing modes in single‐crystal state and optimization of morphology in films by modifying the substitution site of the donor units. As a result, intermolecular π–π interactions are effectively alleviated and a very smooth surface with a reduced defect density is simultaneously achieved, which can significantly reduce the density of triplet excitons, accelerate the charge transfer rate, and enhance carrier injection efficiency. Consequently, a super‐high photoluminescence quantum yield (PLQY) of 99% and fast kRISC of 1.1 × 105 s−1 are concurrently achieved for the proof‐of‐concept emitter 3,4‐Cz‐SF‐SFAC. The corresponding deep‐blue organic light‐emitting diode (OLED) demonstrates an exceptional external quantum efficiency (EQE) of 31.1%, accompanied by an emission peak at 457 nm, one of the preeminent TADF materials within the deep blue region, ranking among the most efficient OLEDs with an EL spectra below 460 nm on record.
Funder
National Science Fund for Distinguished Young Scholars
National Natural Science Foundation of China
Subject
Condensed Matter Physics,Atomic and Molecular Physics, and Optics,Electronic, Optical and Magnetic Materials