Metal oxide nanoparticles are critical components in current efforts to convert sunlight into fuel and electricity. However, the photovoltaic and photoelectrochemical properties of these materials, particularly carrier dynamics, are largely controlled by surface trap states of uncertain chemical origin. In recent work, we have elucidated the spatial and energetic distribution of trap states of nanocrystalline TiO2 using photoluminescence imaging and spectroscopy. By observing photoluminescence of a nanocrystalline TiO2 electrode under Fermi level control, we have determined the redox potentials of intraband gap states in nanosheets and conventional nanoparticles. We have recently explored the dependence of trap state energies of TiO2 nanoparticles in aqueous and nonaqueous environments under Fermi level control. Our results shed light on the well-known dependence of energy conversion efficiency on solvent electrolyte in the case of the dye-sensitized solar cell. This talk will present recent work to exploit spectroelectrochemical photoluminescence to elucidate the effects of potential-determining ions, nanoparticle morphology, and doping on the activity of transport-limiting surface traps of TiO2. Emphasis is on the chemical nature of the traps and what can be learned about how to manage their properties for energy applications.

Illuminating trap states of nanocrystalline titanium dioxide and their role in dye-sensitized solar energy conversion

248th National Meeting (2014)

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