Pyridal[2,1,3]thiadiazole as strong electron-withdrawing and less sterically-hindered acceptor for highly efficient donor–acceptor type NIR materials

Jianxia Jiang; Xianglong Li; Muddasir Hanif; Jiadong Zhou; Dehua Hu; Shijian Su; Zengqi Xie; Yu Gao; Bing Yang; Yuguang Ma

doi:10.1039/C7TC03978F

Pyridal[2,1,3]thiadiazole as strong electron-withdrawing and less sterically-hindered acceptor for highly efficient donor–acceptor type NIR materials†

Jianxia Jiang,^a Xianglong Li,^a Muddasir Hanif,^a Jiadong Zhou,^a Dehua Hu,*^a Shijian Su,

^a Zengqi Xie,^a Yu Gao,^b Bing Yang

^b and Yuguang Ma

*^a

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* Corresponding authors

^a Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, P. R. China
E-mail: msdhhu@scut.edu.cn, ygma@scut.edu.cn
Fax: +86-20-87110606
Tel: +86-20-22236311

^b State Key Laboratory of Supramolecular Structure and Materials, Jilin University, Changchun 130012, P. R. China

Abstract

Pyridal[2,1,3]thiadiazole (PT) is an analogue of benzo[1,2,5]thiadiazole (BT), which is a common acceptor in charge transfer (CT) chromophores. Compared with BT, PT is more electron-deficient and less sterically hindered. Herein we demonstrate the effect of using PT as proto-acceptor in the design of D–A type NIR emitting materials. The compound p-TPA-PT-CN was synthesized, which combines PT with the donor triphenylamine (TPA) and cyano-substituent (CN), and shows NIR emission at ∼700 nm with a high PL efficiency of 0.3 in both solution and solid state. The strong D–A interaction within p-TPA-PT-CN results in a low energy charge-transfer state. The pyridine nitrogen of PT reduces the steric hindrance between PT and the adjacent TPA donor segment, resulting in increased planarity and strong mixing (hybridization) of CT and π–π states (HLCT). Such strong mixing contributes towards a higher luminous efficiency. The OLEDs fabricated with p-TPA-PT-CN as the emitting layer exhibited an EQE of 1.47% and L_max = 640 cd m⁻², which are amongst the highest values reported for NIR-OLED devices.

Journal of Materials Chemistry C

Pyridal[2,1,3]thiadiazole as strong electron-withdrawing and less sterically-hindered acceptor for highly efficient donor–acceptor type NIR materials†

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Pyridal[2,1,3]thiadiazole as strong electron-withdrawing and less sterically-hindered acceptor for highly efficient donor–acceptor type NIR materials

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