Thiophene-based conjugated oligomers for organic solar cells

Owing to their efficient light harvesting, structural versatility and intrinsic charge transport behavior, thiophene-based π-conjugated systems have attracted much attention in developing high performance organic solar cells. In comparison to the relevant conjugated polymers that are used as active materials in photovoltaic devices, conjugated oligomers possess some critical advantages: (1) well-defined molecular structures lead to their synthetic reproducibility with high purity which is vital to obtain repeatable device performance; (2) crystalline features of oligomers favor the long range order in the solid state and benefit the charge carrier transport; (3) the devices can be readily fabricated by both solution-processable and vacuum-deposited techniques. In this feature article, thiophene-based conjugated oligomers with molecular architectures from 1D to 3D, which play an essential role in the device performance of organic solar cells, will be summarized. We aim to address the influence of the thiophene motifs on the electronic, optical and self-assembly properties of the materials, and eventually conclude the relationship between the molecular structures and photovoltaic properties.