Tuning electron affinity by heteroannulation of benzothiadiazole in organic semiconductors Xiantao Hu 1 , Aniruddha Basu 2 , Datt Ram 3 , Qiao He 1 Thomas D. Anthopoulos 2 , Wing Chung Tsoi 3 and Martin Heeney 1 1 Imperial College London, UK, 2 King Abdullah University of Science and Technology, Saudi Arabia 3 Swansea University, UK Remarkable progress has been made in the development of organic semiconductors for flexible electronics like organic field-effect transistor, organic photovoltaics since the initial proposal of alternating donor-acceptor (D-A) systems. In D-A type materials, the energetics can be tuned by rational choice of the D and A components, with the LUMO (lowest unoccupied molecular orbital) largely determined by the acceptor unit. Here we report our effort to develop novel electron-deficient units based on the extensively investigated acceptor unit benzothiadiazole (BT). Different from changing the heteroatom in thiadiazole ring or functionalising the benzo ring to modify the energetics, we adopt an expedient one-step reaction to heteroannulate additional rings to the BT core, extending the conjugation by appending an electron-withdrawing 2-(1,3-dithiol-2-ylidene)malonitrile group. We report the influence of appending the ring to the 5,6-positions, as well as the 4,5-positions. In the former case, a variety of co-polymers are reported which exhibit thermochromic behaviour, ambipolar charge transport and reasonable performance as the semiconducting layer in organic field-effect transistor. 1 In the latter case, small molecule acceptors are synthesized with the modified BT as end-group. The resulting medium band gap materials are examined in blends with various donor polymers and showed good performance in organic photovoltaics. 2 Our findings demonstrate that heteroannulating additional rings by appending the 2-(1,3-dithiol-2-ylidene) malonitrile group is a useful approach to construct electron-deficient units in organic semiconductors. References 1. Synergistic Interaction of Heteroannulation and Fluorination in n-Type Semiconducting Polymers for Organic Field-effect Transistor. X. Hu, A. Basu, Q. He, T. D. Anthopoulus and M. Heeney. (In Preparation) 2. Facile synthesis of annulated benzothiadiazole derivatives and their application as medium band gap acceptors in organic photovoltaic devices. X. Hu, R. Datt, Q. He, P. Kafourou, H. Ka Hin Lee, A. J. P. White, W. C. Tsoi and M. Heeney, Journal of Materials Chemistry C , 2022 , 10, 9249-9256.
P16
© The Author(s), 2022
Made with FlippingBook Learn more on our blog