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Proceedings Paper

Ab initio molecular dynamics of ultrafast electron injection from molecular donors to the TiO2 acceptor
Author(s): William Stier; Walter R. Duncan; Oleg V Prezhdo
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Paper Abstract

The photoinduced electron transfer (ET) from a molecular electron donor to the TiO2 semiconductor acceptor triggering Gratzel solar cells and other photochemical applications is investigated. The reported simulations reproduce the experimentally observed ET time-scale, establish the reaction mechanism, and provide a detailed picture of the ET process. The electronic structure of the chromophore-semiconductor system is simulated by density functional theory (DFT). Ab initio molecular dynamics (MD), including non-adiabatic (NA)transitions between electronic states, NAMD, is used to follow the ET reaction in real-time and at the molecular level. The simulation indicates that thermally driven adiabatic ET s dominant at room temperature. Vibrational motions of the chromophores induce oscillations of the photoexcited state energy that drives the photoexcited state in and out of the TiO2 conduction band. Two distinct types of ET events are observed depending on the initial conditions. At low initial energies the photoexcited state is well localized on the chromophore, and an activation is required for ET, with comparable contributions from both the adiabatic and NA mechanisms. At high initial energies the photoexcited state is already substantially delocalized into the TiO2 substrate. The remaining fraction of the ET process occurs rapidly and by the adiabatic mechanism.

Paper Details

Date Published: 4 December 2003
PDF: 15 pages
Proc. SPIE 5223, Physical Chemistry of Interfaces and Nanomaterials II, (4 December 2003); doi: 10.1117/12.503646
Show Author Affiliations
William Stier, Univ. of Washington (United States)
Walter R. Duncan, Univ. of Washington (United States)
Oleg V Prezhdo, Univ. of Washington (United States)

Published in SPIE Proceedings Vol. 5223:
Physical Chemistry of Interfaces and Nanomaterials II
Tianquan Lian; Hai-Lung Dai, Editor(s)

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