Steric and Solvent Effect in Dye-Sensitized Solar Cells Utilizing Phenothiazine-Based Dyes

Abstract

Three phenothiazine-based dyes have been prepared and utilized as dye-sensitized solar cells (DSSCs). The effects of dye-adsorption solvent on the performances of dye-sensitized solar cells based on phenothiazine dyes were investigated in this study. The highest conversion efficiency of 3.78% was obtained using ethanol (EtOH) and 2.53% for tetrahydrofuran (THF), respectively, as dye-adsorption solvents. Cell performance using EtOH as a dye-adsorption solvent showed relatively higher performance than that using THF. Electrochemical and photochemical tests of phenothiazine dyes in solution and adsorbed on the TiO ₂surface showed less dye loading and coverage on the TiO ₂surface during adsorption in the case of THF, which decreased the solar cell performance of the DSSC using THF as adsorption solvent compared with using EtOH as adsorption solvent. Meanwhile, the steric effect of phenothiazine-based ( PT1–3) dyes was also investigated. Dye with longer and branched aliphatic chain in the order of PT1, PT2, and PT3showed an increased resistance of the recombination reaction and electron lifetime, thereby increasing $V_{\text{oc}}$and enhancing the overall cell performance because of the sterically hindered conformation of the phenothiazines.