Solar energy applications require understanding of dynamical response of novel materials on nanometer scale. Our state-of-the-art non-adiabatic molecular dynamics techniques, implemented within time-dependent density functional theory, allow us to model such response at the atomistic level and in real time. The talk will focus on photoinitiated charge transfer at the interfaces of bulk TiO2 with a variety of systems, including organic molecules, water, semiconductor quantum dots (QDs), and graphene. Photoinduced charge separation across molecular/bulk interfaces drives dye-sensitized semiconductor solar cells. It creates many challenges due to stark differences between molecular and periodic systems. QDs are quasi-zero dimensional structures with a unique combination of molecular and bulk properties. They exhibit new physical phenomena, including phonon bottleneck and multiple exciton generation, with the potential to increase solar cell efficiency. Graphene is an excellent conductor. At the same time, it has zero band-gap, and photoexcited electrons and holes can rapidly lose all energy by coupling to phonons, resulting in complete photovoltaic efficiency loss.  We are able to characterize the rates and branching ratios of the competing processes. Our simulations provide a unifying description of quantum dynamics on nanoscale, resolve highly debated issues, and generate theoretical guidelines for development of novel systems for energy harvesting.

Solar energy harvesting and photoinduced charge separation at TiO<sub>2</sub> interfaces: Insights from time-domain ab initio simulations

246th National Meeting (2013)

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Solar energy harvesting and photoinduced charge separation at TiO2 interfaces: Insights from time-domain ab initio simulations

Solar energy harvesting and photoinduced charge separation at TiO₂ interfaces: Insights from time-domain ab initio simulations