Cost-effective dyes based on low-cost donors and Pd-free synthesis for dye-sensitized solar cells

The structural design of photosensitizers for dye-sensitized solar cells (DSSCs) usually involves modification of the donor and π-spacer moieties using expensive Pd crosscoupling reactions. Herein, the concept of more sustainable and cost-effective dyes to realize large-scale production is presented. Two dyes, coded BzC and PTZC, with low-cost donors, phenyl and phenothiazine, respectively, and 4H-cyclopenta[2,1-b:3,4-b’]dithiophene π-spacer, are synthesized by Pd-free reactions, including Horner–Wadsworth–Emmons, with high overall yield (68% for BzC and 55% for PTZC). The best photovoltaic performances exhibit 3.00% and 5.92% together with relatively low ideality factor of 1.03 and 1.12 for BzC and PTZC, respectively, indicating efficient retardation of electron recombination from surface trap states. Finally, the synthesis costs for BzC and PTZC are estimated to be about 7.5–9 times lower than that of LEG-4 (as a commercial reference dye). The cost performances of BzC and PTZC are estimated to be around 5 times better than that of LEG-4.