New organic sensitizers using 4-(cyanomethyl)benzoic acid as an acceptor group for dye-sensitized solar cell applications

Two design elements for donor-acceptor organic dyes used in dye-sensitized solar cells (DSSCs) are presented. 4-(Cyanomethyl)benzoic acid was used as an acceptor group and was compared to the commonly used cyanoacrylic acid acceptor group in a pair of otherwise structurally equivalent sensitizers. The 4-(cyanomethyl)benzoic acid based dyes showed significantly improved photovoltaic performance when tested in DSSCs. Furthermore, it was shown that the replacement of the bridging paraphenyl group with a thiophene group in triarylamino-oligothiophene-based sensitizers resulted in a significant spectral red-shift and improved device performance when tested in DSSCs. DSSCs that were constructed using a sensitizer embodying both the design features show an increase in electron lifetime when compared with DSSCs fabricated using conventional sensitizer. The most promising of the novel dyes incorporating both the design features displayed a power conversion efficiency of 6.37%, short circuit photocurrent density of 11.63 mA cm-2, open-circuit voltage of 0.754 V and fill factor of 0.73.