Design and Development of New Indole Based Sensitizers for Dye Sensitized Solar Cells

Abstract

Solar energy is regarded as the holy grail of renewables owing to its abundant availability and pollution-free character. The conversion efficiency of Si based cells is currently around 20%. But these cells are expensive and involve energy-intensive fabrication process. Further, their rigid shape confines them to specific applications. Ever since the pioneering report by O’Regan and Graztel in 1991, dye-sensitized solar cells (DSSCs) have emerged as credible alternative to conventional silicon-based solar cells due to their low cost, moderate efficiency and easy fabrication techniques. At present, there is a considerable interest among the researchers to develop new and efficient sensitizers for DSSC application. In this context, it was contemplated to design, synthesize and to investigate the photovoltaic performance of new indole based sensitizers and co-sensitizers. Based on the detailed literature survey, new indole sensitizers were designed as potential sensitizers/co-sensitizers. They were later successfully synthesized following the appropriate synthetic routes. Further, their synthetic methods as well as purification techniques were established and their yields were optimized. Furthermore, their structures were confirmed by various spectral techniques. Finally, the target compounds were characterized for their optical, electrochemical and photovoltaic performance studies. The photovoltaic performance studies of the newly synthesized sensitizers reveal that molecules carrying 4-aminobenzoic acid exhibit better photovoltaic performance than their cyanoacetic acid based counterparts. Further, the devices fabricated by incorporating the aforementioned co-sensitizers exhibit superior performance than the cells fabricated using only the ruthenium based sensitizer. In addition, the effect of anchoring groups on the co-sensitizer performance has been investigated. The highest efficiency obtained by the sensitizers synthesized in this work is 4.12 %, whereas, the highest efficiency obtained by a co-sensitized cell is 10.68%.To sum up, new indole derivatives appeared as active templates for highly efficient metal-free sensitizers/co-sensitizers.