Progress in flexible dye solar cell materials, processes and devices

Flexible Dye Solar Cells (FDSCs), in their most widespread architecture, are assembled with two opposing planar films or foil substrates in metal–plastic or plastic–plastic combinations. The use of one metal electrode enables the convenient utilization of materials and high temperature processes but is accompanied by issues including partial opacity of the electrolyte and catalyst layer. Constraints on the stability of plastic substrates have led to the development of a variety of alternative material formulations and processes to guarantee performance even at low temperatures compatible with plastic films. Recently, efforts in doing without transparent conducting oxides have led to the development of new unconventional architectures. Review of the operation of DSCs shows that initial target markets are represented by indoor applications where power output densities have been shown to outperform competing flexible photovoltaic technologies. Whereas performance, stability in particular, needs to be significantly improved for the adoption in long term outdoor installations, commercial products integrating FDCSs for indoor or portable use have already been launched. Issues pertaining progress in materials, processes, devices and industrialization of FDSCs will be analyzed and discussed in this review.