Conjugated polymers and small molecules containing the thiophene–vinylene–thiophene (TVT) unit for organic photovoltaic applications

Abstract

Thiophene–vinylene–thiophene (TVT) is a well-known building block of organic photovoltaic materials because of its tunable optical absorption, strong molecular aggregation, and high charge mobility. Recently, TVT-based materials attracted much more attention because promising power conversion efficiency (PCE) of over 16% has been reported. This review comes to being and will sum up the TVT-based conjugated polymers and small molecules in which TVT can serve as either an electron-donating unit or an electron-accepting unit according to its substituents and also can act as a π bridge unit in these materials. The main content elaborated includes molecular structures, charge generation, transport, and collection properties, energy loss, molecular stacking, and blend film morphology. In particular, the contribution of molecular stacking originating from the enhanced molecular rigidity caused by the introduction of non-covalent interaction will be emphasized. Of note is that the carboxylate-containing TVT-based polymers show reduced non-radiative energy loss compared to their counterparts without carboxylate. And both polymers and small molecule acceptors based on Y-series small molecules using TVT as the linkage unit present a wide absorption window, homogeneous phase composition, and high charge mobility. In addition, the TVT material-based all-polymer and ternary OPVs which exhibited satisfactory PCE have also been discussed.