Organic d-π-a dyes for dye-sensitized solar cell

Dye-sensitized solar cells (DSSCs) have received considerable attentions as a cost-effective alternative to conventional solar cells. One of main issues for the development of DSSCs is the design and synthesis of dyes that serve as light absorbers for energy conversion. Up to now, many different pure organic dyes and transition metal complexes have been evaluated as sensitizers. DSSCs sensitized with pure organic dyes have relatively lower power conversion efficiencies than those sensitized with metal complexes. However, pure organic dyes have many advantages for their application in DSSCs, such as lower cost, higher absorption coefficient and easy control of redox potentials of LUMO and HOMO levels. Importantly, the highest power conversion efficiency of DSSCs with pure organic dyes has reached 8.0%, which is close to that (similar to 10%) of DSSCs with metal complexes. In this paper, the features of pure organic dyes and several ways for the design towards higher efficiency are presented. The recent progress on the selection and utilization of these pure organic dyes, especially organic D-pi-A dyes, are mainly discussed. The effects of the structures of organic D-pi-A dyes on cell performances are compared.