Effects of solvents and substituents on the adsorptive and photovoltaic properties of porphyrins for dye-sensitized solar cell application: a theoretical consideration

The adsorptive properties onto TiO2 film, and the solubility behaviors of eighteen porphyrin derivatives in acetonitrile (AcCN), dichloromethane (DCM), dimethyl sulphoxide (DMSO), and ethanol (EtOH) have been predicted using thermodynamic data obtained from density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations. The computed photovoltaic (PV) properties were found to be enhanced with -CO2H group as the substituent of the parent porphyrin, and AcCN or DCM as solvent. The adsorption properties of the porphyrins on the TiO2 surface as predicted, were just about 22% similar to the computed solubility properties in the selected solvents. The poor correlation observed between the two parameters is a result of the porphyrin-solvent-TiO2 interaction which is present for adsorption, but absent for solubility. The described method could be employed for the design of efficient porphyrin-solvent systems for DSSC application.