Influence of terminal imide units on properties and photovoltaic characteristics for benzothiadiazole-based nonfullerene acceptors

Abstract

Development of new semiconducting materials has become an important subject to develop organic photovoltaics. In this letter, new electron-accepting π-conjugated molecules, which are composed of thiophene-linked benzothiadiazole (T-BTz) as a central unit and phthalimide (PI) or naphthalimide (NI) as a terminal unit, were designed and synthesized to investigate the influence of the terminal units on the properties and photovoltaic characteristics. The utilization of NI led to red-shifted absorption and increased electron-accepting characteristics, compared to those of PI. Furthermore, the photovoltaic device based on T-BTz-NI under the combination with poly(3-hexylthiophene) as a donor showed improved power conversion efficiency of 1.16%. These results indicate that NI become a good candidate for a terminal unit of non-fullerene acceptors.