First-Principle Determination of Electronic Coupling and Prediction of Charge Recombination Rates in Dye-Sensitized Solar Cells

Abstract

In the study of dye-sensitized solar cells (DSCs), developing computational predictions of key properties of the dyes is highly desirable for identifying promising candidates. In this work, we report first-principle-based, theoretically estimated charge-recombination (CR) rates from TiO2 to the cationic dye for 2 pairs of organic dye molecules. A recently developed multistate fragment charge difference (msFCD) scheme, together with long-range-corrected time-dependent density functional theory, was used to calculate the electronic coupling. The msFCD scheme removes the local excitation components in the charge-transfer states, and generates acceptable diabatic states. The range-separated ωPBE and BNL functionals were useful for the charge-transfer problem, and results were largely independent of TiO2–dye binding modes. The rates obtained for CR to oxidized dye (CRD) followed a trend similar to experimental results. In general, a difference in the reorganization energy (λ) and the free energy (ΔG0) had a la...