Thermally Enhanced and Long Lifetime Red TADF Carbon Dots via Multi‐Confinement and Phosphorescence Assisted Energy Transfer

• Published in: Advanced materials (Weinheim) Vol. 35; no. 20; pp. e2211858 - n/a
• Main Authors: Lou, Qing, Chen, Niu, Zhu, Jinyang, Liu, Kaikai, Li, Chao, Zhu, Yongsheng, Xu, Wen, Chen, Xu, Song, Zhijiang, Liang, Changhao, Shan, Chong‐Xin, Hu, Junhua
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.05.2023
• Subjects: Activated carbon; carbon dot; Carbon dots; Decay rate; Emission; Energy transfer; Excitons; High temperature; Ionic crystals; Materials science; Phosphorescence; TADF; Temperature dependence; thermally enhanced luminescence; Time dependence; time‐/temperature‐dependent delayed emission; TADF; energy transfer; time-/temperature-dependent delayed emission; carbon dot; thermally enhanced luminescence
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202211858

Thermally activated delayed fluorescence (TADF) materials, which can harvest both singlet and triplet excitons for high‐efficiency emission, have attracted widespread concern for their enormous applications. Nevertheless, luminescence thermal quenching severely limits the efficiency and operating stability in TADF materials and devices at high temperature. Herein, a surface engineering strategy is adopted to obtain unique carbon dots (CDs)‐based thermally enhanced TADF materials with ≈250% enhancement from 273 to 343 K via incorporating seed CDs into ionic crystal network. The rigid crystal network can simultaneously boost reverse intersystem crossing process via enhancing spin‐orbit coupling between singlet and triplet states and suppressing non‐radiative transition rate, contributing to the thermally enhanced TADF character. Benefiting from efficient energy transfer from triplet states of phosphorescence center to singlet states of CDs, TADF emission at ≈600 nm in CDs displays a long lifetime up to 109.6 ms, outperforming other red organic TADF materials. Thanks to variable decay rates of the delayed emission centers, time and temperature‐dependent delayed emission color has been first realized in CDs‐based delayed emission materials. The CDs with thermally enhanced and time‐/temperature‐dependent emission in one material system can offer new opportunities in information protection and processing. A surface engineering strategy is developed to confine carbon dots into a rigid network derived from multiple ionic bonds, which efficiently promote reverse intersystem crossing rate, suppress non‐radiative transition, and stabilize triplet excited states. These results endow carbon dots with unique thermally enhanced TADF luminescence, accompanied by a long lifetime via energy transfer from RTP donor.