Ab Initio Determination of Ground and Excited State Oxidation Potentials of Organic Chromophores for Dye-Sensitized Solar Cells

Abstract

Ab initio calculations of the ground state oxidation potential (GSOP) and excited state oxidation potential (ESOP) are reported for a set of four triphenylamine-based dyes for dye-sensitized solar cell (DSSC) applications, with increasing degree of charge transfer. The performance of DFT in predicting GSOP is evaluated by employing various exchange-correlation (x-c) functionals, with different amounts of Hartree−Fock exchange and different combinations of correlation functionals. The choice of the correlation part of the x-c functional was crucial in getting accurate GSOPs. For excited state geometry optimizations, needed to calculate the adiabatic excitation energies E0−0 and therefore the ESOPs, the use of hybrid functionals with a large amount (∼50%) of nonlocal Hartree−Fock exchange has been shown to be mandatory to avoid the formation of artificial minima in correspondence of a twisted geometries with a high degree of charge transfer. Our results show that a proper DFT/TDDFT approach can provide a re...