Herein, we report the design and synthesis strategy of a new class of five EDOT based co-sensitizers (CSGR1-5) by introducing different donors (2,3,4-trimethoxypheny, 2,4-dibutoxyphenyl, and 2,4-difluorophenyl) and anchoring groups (rhodamine-3-acetic acid and cyanoacetic acid) systematically. The synthesized metal-free organic co-sensitizers were employed for cocktail dye-sensitized solar cells along with N749 (black dye). The DSSC devices with a mixture of co-sensitizers (CSGR1-5) and N749 have shown a 7.95%, 8.40%, 7.81%, 6.56% and 6.99% power conversion efficiency (PCE) respectively, which was more than that of single N749 dye PCE (6.18%). Enhanced efficiency could be ascribed to the increased short circuit current (Jsc) and open circuit voltage (Voc). The increased Jsc was achieved due to enhanced light harvesting nature of N749 device upon co-sensitization with CSGR dyes and feasible energy levels of both the dyes. The Voc was improved due to better surface coverage which helps in decreasing the rate of recombination. The detailed optical and electrochemical properties were investigated and complimented with theoretical studies (DFT).
Keywords: 3,4-ethylenediox-thiophene; DFT; co-sensitizer; dye-sensitized solar cells; power conversion effiecency.