A DFT Study of Solvent and Substituent Effects on the Adsorptive and Photovoltaic Properties of Some Selected Porphyrin Derivatives for DSSC Application.

Abstract

A DFT/TD-DFT method was employed to study the effects of structural modification and solvent variation on the solubility, adsorptive, and photovoltaic properties of six porphyrins (A-F) obtained by structurally modifying two literature porphyrins A and D. The properties of interest were studied in vacuum, acetonitrile (AcCN), dichloromethane (DCM), dimethyl sulphoxide (DMSO), and ethanol (EtOH) for possible application of the molecules as sensitizers in dye-sensitized solar cells (DSSCs). Electronic absorption properties of the molecules were computed via potential energy surface scan, and thermodynamic data were obtained by DFT calculations in the selected media. Solubility properties of the molecules were mostly enhanced with DMSO as the solvent. The adsorptivity of the molecules onto mesoporous titanium (IV) oxide surface were predicted to be enhanced in the presence of DMSO. Most of the molecules were found to exhibit their highest photovoltaic activity measured in terms of the incident photon conversion efficiency (IPCE) in AcCN and DCM, rather than in DMSO due to its high viscosity and the ability to use its oxygen to form the catenating O-Ti⁴⁺ bond with the Ti⁴⁺ of the TiO₂, causing inhibition of electron movement on the semiconductor surface. In general, the computed photovoltaic (PV) properties were found to be enhanced with -CO₂H group as the substituent, and in AcCN or DCM as the solvent.