Highly efficient deep-red TADF organic light-emitting diodes via increasing the acceptor strength of fused polycyclic aromatics
| Autor: | Qi-Sheng Tian, Jian-Li He, Fan-Cheng Kong, Bangjin Sun, Xiao-Jing Wang, Jian Fan, Liang-Sheng Liao |
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| Rok vydání: | 2021 |
| Předmět: |
Photoluminescence
Materials science Band gap General Chemical Engineering Phenazine 02 engineering and technology General Chemistry 010402 general chemistry 021001 nanoscience & nanotechnology Internal conversion (chemistry) Photochemistry 01 natural sciences Fluorescence Acceptor Industrial and Manufacturing Engineering 0104 chemical sciences chemistry.chemical_compound chemistry Excited state OLED Environmental Chemistry 0210 nano-technology |
| Zdroj: | Chemical Engineering Journal. 424:130470 |
| ISSN: | 1385-8947 |
| Popis: | Deep-red and near-infrared organic light-emitting diodes (DR/NIR-OLEDs) showed a wide range of applications such as healthcare and night-vision. However, red emitters generally demonstrated severe non-radiative emission due to energy gap law, and the development of efficient deep-red and near-infrared thermally activated delayed fluorescence (DR/NIR-TADF) materials was still under-researched by now. Herein, we designed and synthesized a series of efficient red/DR TADF emitters. Their emission wavelengths were rationally regulated into DR region via introducing strong electron-withdrawing groups from pyridinyl (PY) to trifluoromethyl (CF3) and to cyano (CN). The internal conversion (IC) process of these emitters was suppressed greatly via the incorporation of fused polycyclic aromatics (dibenzo[a,c]phenazine). Furthermore, the structural relaxation of their excited states was also reduced due to the restricted σ bond rotation between donor (D) and acceptor (A) units. As a result, these red/DR emitters showed high photoluminescence quantum yields (PLQYs) and excellent electrofluorescence performance. Particularly, OLEDs based on CN-TPA showed remarkably high maximum external quantum efficiencies (EQEs) of 22.80% at 668 nm, 18.41% at 688 nm and 15.05% at 698 nm, which were among the best values for reported TADF emitters. This result may provide a straightforward design strategy for efficient DR/NIR TADFs through optimizing the acceptor strength of rigidified polyaromatic frameworks. |
| Databáze: | OpenAIRE |
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