Competitive Intermolecular Energy Transfer and Electron Injection at Sensitized Semiconductor Interfaces

Abstract

Sensitization of nanocrystalline TiO{sub 2} electrodes with molecular chromophores forms the basis for efficient solar energy conversion in regenerative photoelectrochemical cells. The study of interfacial electron-transfer dynamics in these solar cells is an area of intense and active investigation. The nanocrystalline materials also have the potential to act as supports for molecular reagents and could increase the efficiency of reactions that are otherwise limited by diffusive encounters in fluid solution. The ability to photoinduce interfacial electron transfer coupled with exploitation of lateral reaction chemistry will produce materials that have applications that extend beyond solar energy conversion. Here the authors report an unprecedented example of molecular excited states that can be switched from lateral energy transfer across a nanocrystalline TiO{sub 2} surface to orthogonal interfacial electron injection by electrolyte modification or with an externally applied potential. Significantly, the process is reversible and serves as a molecular charge-energy transfer switch.