Cosensitization of a Tetraethylene Glycol‐Substituted Unsymmetrical Zinc Phthalocyanine Sensitized Solar Cells with D131 Auxiliary Dye Exhibited Enhanced Efficiency

Abstract An asymmetric zinc phthalocyanine dye (ZnPcT 3 C), bearing three tetraethylene glycol donor groups and one carboxylic acid anchoring group, was synthesized as a photosensitizer dye for dye‐sensitized solar cells (DSSCs). The tetraethylene glycol (TEG), consisting of four ethoxy units, works as an amphiphilic long‐chain donor group that greatly helped in reducing the molecular aggregation. Carboxylic acid group, on the other hand, an acceptor, together with TEG in ZnPcT 3 C functions as a ‘push–pullʼ system suitable for DSSCs. Absorption spectra of ZnPcT 3 C in DMSO showed a strong sharp Q band in the infrared region 600–700 nm with ( λ max = 682 nm) and a less intense soret band appeared in the region 300–400 nm with λ max = 340 nm. The zinc phthalocyanine (ZnPcT 3 C) exhibited molar extinction coefficient ( ε ) of 72,727 L mol −1 cm −1 . The emission was observed at λ em = 695 nm upon excitation at 650 nm and exhibited a fluorescence decay of 2.82 ns. The ZnPcT 3 C dye sensitised solar cell ( c = 1 mM) exhibited the power conversion efficiency ( η ) of 3.52% in chloroform in I − /I 3 electrolyte under simulated 100% brightness. Cosensitization of ZnPcT 3 C with another auxiliary dye D131 in 1:1 ratio in a cocktail‐type DSSC attained the power conversion efficiency of twice as high as η = 6.27% in an identical condition. A mixture of D131 ( λ max = 470 nm) dye with the ZnPcT 3 C phthalocyanine harvests sunlight across the visible spectra, enabling DSSCs to attain a large photocurrent and photovoltage, enhancing power conversion efficiency.