Automated redox potentials assessment of dyes for photelectrochemical cells
Dye-sensitized photoelectrochemical cells (DS-PEC) are promising systems for sustainable fuel production. A great advantage for their design is the modularity of these systems. In particular, it is of interest to tune the dye’s optical and electrochemical properties, such as their ground state oxidation potential (GSOP), by slight structural adjustments. In a recent paper, a fast and automated workflow has been suggested for the automated screening of thousands of candidate molecules to identify promising dyes.
To design this workflow many state-of-the-art electronic structure methods have been evaluated, as well as different approaches that calculate the GSOP either as the Gibbs free energy of the oxidation reaction (difference between the solution-phase Gibbs free energies of the products and reactants) or as the vertical ionization energy of the solvated dye.
Solution-phase Gibbs free energy were calculated with DFT, including solvent effects with COSMO or COSMO-RS. Also, approximations of the GSOP by vertical ionization potentials, calculated at the Kohn-Sham and the GW level have been assessed. For perylene type of dyes, considering geometry relaxation after oxidation and electronic solvent effects is of high importance, while other thermal effects can be neglected. Combining accuracy and computational efficiency, the optimal workflow consists of geometry optimization performed using fast density-functional based tight binding methods (GFN1-xTB), single point DFT calculation including COSMO, and a COSMO-RS thermodynamic calculation (see python scripting examples).
