Evaluation of computational approaches to design new photosensitizers

From dye-sensitized solar cells to photodynamic therapy, the design of new photosensitizers involves different computational strategies. In this work, we present selected examples aiming at illustrating the limitations and advantages of each selected strategy, as well as listing useful descriptors. Hybrid functionals are reasonable approaches to determine properties related to the electronic absorption spectrum; however, for metallic complexes such as metalloporphyrins, one may be careful in selecting the DFT approach. Self-aggregation of dyes is a phenomenon the experimentalists try to avoid, and it is essential to include dispersion corrections and solvation effects to understand the energetics of this process. Aggregation may be driven by π-stacking or hydrophobic effects, depending on the dye composition. Besides all those characteristics, the design of a new photosensitizer may involve evaluating substitution and anchoring groups, push-pull effects, photostability, and reaction mechanisms in the excited states.