Co-sensitization of HD-2 complex with low-cost cyanoacetanilides for highly efficient DSSCs

The photophysical and electrochemical properties of new-targeted 2-cyanoacetanilide-based dyes are illustrated. The new cyanoacetanilides SA7-10 were synthesized and employed as co-sensitizers in DSSCs. The chemical structures of these 2-cyanoacetanilides differ according to the substituent at benzene ring (-H, -Me, -OMe and -NEt2) keeping the same anchoring moiety –COOH group. Further, density functional theory (DFT) calculation has shown an effective intermolecular charge transfer character, the HOMOs of SA7-10 are mainly located on the corresponding donor part, and their LUMOs are on carboxylic acid moieties as acceptor. Interestingly, using photosensitizers SA7-10 as co-sensitizers with HD-2 dye causes an improvement in its photovoltaic performances. Among the dyes, SA10 co-sensitized with HD-2 displayed an overall efficiency of 8.25%, JSC of 19.5 mA.cm-2, VOC of 0.65 V and FF of 64.35 compared to 7.46%, 19 mA.cm-2, 0.64 V and 60.54 of HD-2 only. Moreover, electrochemical impedance spectroscopy (EIS) data of SA7-10 and HD-2 were found to be in accordance with obtained photovoltaic parameters. Finally, the results indicated that 2-cyanoacetanilide-based dyes were utilized as promising co-sensitizers due to their easily preparation methods and their relatively small size.