A method to rapidly predict the charge injection rate in dye sensitized solar cells

A technique to predict the rate of electron transfer between a chromophore and the TiO2 semiconductor surface in dye sensitized solar cells (DSSC) is presented. The rate is computed by partitioning the system into molecular and semiconductor states and computing the retarded Green's function for the system. A number of recently reported organic chromophores are considered and the results are rationalized in terms of the orbital shape and the energy alignment between molecular and semiconductor states. The method is designed to allow a rapid scanning of potential chromophores as the expensive components of the calculation (computing the density of states on the TiO2 surface and the coupling between these states and the molecule) are performed once for all chromophores with similar adsorption chemistry. With this technique it is possible to predict the rate of injection of a new chromophore in a few hours using a desktop computer and routine quantum chemistry packages.