Dye Sensitized Solar Cells: A Review

The development of dye sensitized solar cells (DSSCs), which have derived inspiration from photosynthesis, has opened up exciting new possibilities and paradigms for producing solar photovoltaics possibly at lower cost. The dye-sensitized solar cells with moderate power conversion (similar to 10%) efficiencies can be manufactured under regular lab conditions without needing clean rooms or very specialized facilities. The entire processing need not involve even a single vapour deposition step. The DSSCs can be considered to be electrochemical devices consisting of (a) a photoanode which has a thick film of a wide band gap oxide semiconductor (like TiO2), typically coated on a transparent conductive oxide (TCO) glass substrate, with TiO2 being sensitized with adsorbed dyes that absorb visible light, (b) an electrolyte that establishes the internal electrical continuity between anode and counter electrode and mainly plays the role of regenerating the dye such that the photoexcitation, electron injection and current flow continues, (c) the counter electrode which is also usually a TCO coated transparent substrate with a suitable catalytic material deposited over it to facilitate efficient charge (electron) transfer from external connection to the electrolyte, (d) sealants to seal the cell assembly containing the electrolyte and prevent ingress of atmospheric influences that may interfere with functioning of the DSSC. The present review describes research that has been carried out and continues on various aspects of DSSCs including developing greater understanding of the basic mechanisms involved, use of new materials, processing techniques and their impact on performance of the cells. A number of challenges are yet to be overcome to realize commercialization of the DSSCs which appears imminent in the near future.