Benzonitrile-based AIE polymer host with a simple synthesis process for high-efficiency solution-processable green and blue TADF organic light emitting diodes

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2022-02, Vol.1 (6), p.219-212
• Main Authors: Zhou, Tao, Zhang, Kaizhi, Cao, Qingpeng, Xu, Hui, Ban, Xinxin, Zhu, Peng, Li, Qile, Shi, Linxing, Ge, Fengjie, Jiang, Wei
• Format: Article
• Language: English
• Subjects: Benzonitrile; Boiling points; Chemical synthesis; Copolymerization; Emitters; Excitons; Fluorescence; Noble metals; Organic light emitting diodes; Polymers; Quantum efficiency; Quenching
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d1tc05010a

Polymer host materials have great potential for enabling small molecular thermally activated delayed fluorescence (TADF) emitters to construct solution-processed organic light-emitting diodes (OLEDs). Herein, four novel benzonitrile-based polymer hosts, P4CzCN-PA, P4CzCN-BCz (1 : 4), P4CzCN-BCz (1 : 1) and P4CzCN-BCz (4 : 1), with TADF characteristics and simple synthesis processes are fully characterized. All the polymers have high triplet energies (>2.68 eV) for effective exciton confining and AIE property for suppressing exciton quenching. By using homopolymerized P4CzCN-PA as the host material, the solution-processed green and blue TADF-OLEDs achieved the maximum external quantum efficiency (EQE) as high as 20.9% and 13.4%, respectively, which are almost 6 times higher than its copolymerized counterpart. This result demonstrates that the TADF polymer host with AIE property can inhibit its concentration quenching without the need for a complicated copolymerization of the bulky monomer. As far as we know, this is the first report of a benzonitrile-based TADF polymer and the final cost of the polymer is lower without any noble metal catalyst or high boiling point solvent. This strategy of using a benzonitrile-based homopolymer as the host materials of OLEDs provides a direction for the design of easy synthesis and low-cost polymer host materials in the future. Polymer host materials have great potential for enabling small molecular thermally activated delayed fluorescence (TADF) emitters to construct solution-processed organic light-emitting diodes (OLEDs).