Large Enhancement of Dye Sensitized Solar Cell Efficiency by Co-sensitizing Pyridyl- and Carboxylic Acid-Based Dyes

Abstract

Co-sensitization is an attractive approach to enhance the light-harvesting efficiency of a dye sensitized solar cell (DSSC), whereby two or more dyes having complementary absorption spectra are co-adsorbed within a DSSC. A new method of co-sensitizing simultaneously pyridyl- and carboxylic acid-based dyes was performed and proved to be a successful approach for increasing the photoconversion efficiency (PCE%) of a DSSC. Yellow and red pyridyl-based dyes (T181 and T202) were co-sensitized with a blue carboxylic acid-based dye (Dyenamo Blue, DB). The co-sensitized DSSCs showed profound performance enhancements with a cobalt tris(bipyridine) electrolyte system. Increases in the total cell efficiency of 45% and 16% were seen in the co-sensitized T181-DB and T202-DB cells when compared to the single dye-sensitized DB cell, respectively. Remarkable increases in photocurrent (Jsc) and photovoltage (Voc) were seen in both co-sensitized cells. The higher Voc values were mainly due to the decrease in the electron recombination processes at the TiO2/cobalt electrolyte interface. The increase in dye coverage in the co-sensitized cells resulted in a blocking behavior at the TiO2/electrolyte interface and had positive effects on electron lifetime. In addition the higher Jsc values were associated with the complementary absorption responses of T181 and T202 with DB as mirrored in the IPCE% spectra. © 2018 American Chemical Society.