Molecular Engineering of Pyrene-Based Co-Sensitizers for High-Performance Dye-Sensitized Solar Cells

A set of pyrene-based dyes (RN-1 to RN-4), each incorporating a distinct electron-withdrawing group, was synthesized and evaluated as co-sensitizers with a commercial black dye in dye-sensitized solar cells (DSSCs). By varying the anchoring units, rhodanine-3-acetic acid, 4-(2-cyanoacetamido)benzoic acid derivative, N-ethylcarbazole-3-acrylamide derivative, and thiazolidinone, this study examined how the molecular structure influences light absorption, electrochemical properties, and device performance. Co-sensitized devices with black dye showed broader and stronger absorption across the visible range, and electrochemical measurements confirmed favorable energy levels for both electron injection as well as dye regeneration processes. Among the series, (RN-2 + black dye) yielded the highest efficiency, reaching 11.40%, a 24% increase over the black dye alone. This improvement is linked to the strong electron-withdrawing character in addition to an effective TiO2 binding of the 4-(2-cyanoacetamido)benzoic acid derivative moiety. Impedance and photon-to-current efficiency (IPCE) analyses further supported the reduced charge recombination and enhanced photocurrent. These results underscore the significant influence of anchoring group selection on solar cell efficiency through its impact on interfacial charge dynamics.