A 2013 paper by the Lee group uses THF when optimizing the geometries of their Zinc Porphyrin based dyes using DFT calculations. I'd say this is a pretty good solvent choice because it is aprotic and the material is probably pretty soluble in THF. I attached the paper below.
In my opinion, the main thing you will want to consider when selecting the solvent for the calculation is that the porphyrin does not undergo aggregation-caused quenching in the selected solvent.
It well known that solar cell efficiencies are affected by the molecular spacer connecting the dye(ZnP) to the semiconductor surface, the sensitization conditions (solvent and time), and the nature of the terminal group of the ZnP.Alcohol/water may be efficient solvent for ZnP.