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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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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 Lmax = 640 cd m−2, which are amongst the highest values reported for NIR-OLED devices.

Graphical abstract: 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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Publication details

The article was received on 31 Aug 2017, accepted on 06 Oct 2017 and first published on 09 Oct 2017


Article type: Paper
DOI: 10.1039/C7TC03978F
Citation: J. Mater. Chem. C, 2017, Advance Article
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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

    J. Jiang, X. Li, M. Hanif, J. Zhou, D. Hu, S. Su, Z. Xie, Y. Gao, B. Yang and Y. Ma, J. Mater. Chem. C, 2017, Advance Article , DOI: 10.1039/C7TC03978F

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