Electron hopping between molecular photosensitizers on semiconductor surface in solar energy conversion and storage devices
Molecular photosensitizers have been attracted intense interest in solar energy conversion and storage devices, such as solar cells and solar fuel devices. On a photocathode, the photosensitizer can be reduced after getting electron from the p-type semiconductor. In a conventional understanding, the reduced photosensitizer will transfer electron to either an electrolyte in solar cell or a catalyst in a solar fuel devices. However, if there is strong electron coupling between each molecular photosensitizer, an electron hopping process could exist among many other surface charge transfer processes such as dye regeneration by redox couple or catalyst and charge recombination between reduced photosensitizer and p-type semiconductor. If an electron hopping contributes charge transfer kinetics in any of these processes, it is a very interesting scientific questions. It will also help us to improve the performance of these devices. We will study this topic from both experimental and theoretical ways. From the experiment, we will use electrochemical method to reduce the photosensitizer on semiconductor surface to get the apparent electron hopping rate. However, it is hard for us to get the real arrangement and interactions of these photosensitizers on the p-type semiconductor surface. Therefore, we need to get help from the DFT calculation. We will calculate the electron hopping with different photosensitizer arrangement between each other on surface and compare the computational results with experimental data. This study has not been done before by any other groups. The obtained understanding will help us to design the photosensitizer as well as construct the photocathode for solar energy conversion and storage.