title: Ab Initio Simulation of the Absorption Spectra of Photoexcited Carriers in TiO2 Nanoparticles.
abstract: We investigate the absorption spectra of photoexcited carriers in a prototypical anatase TiO2 nanoparticle using hybrid time dependent density functional theory calculations in water solution. Our results agree well with experimental transient absorption spectroscopy data and shed light on the character of the transitions. The trapped state is always involved, so that the SOMO/SUMO is the initial/final state for the photoexcited electron/hole absorption. For a trapped electron, final states in the low energy tail of the conduction band correspond to optical transitions in the IR, while final states at higher energy correspond to optical transitions in the visible. For a trapped hole, the absorption band is slightly blue-shifted and narrower in comparison to that of the electron, consistent with its deeper energy level in the band gap. Our calculations also show that electrons in shallow traps exhibit a broad absorption in the IR, resembling the feature attributed to conductive electrons in experimental spectra.
authors: Computational Laboratory of Hybrid/Organic Photovoltaics (CLHYO), CNR-ISTM, via Elce di Sotto 8, I-06123 Perugia, Italy.|Department of Chemistry, Biology and Biotechnologies, Universitá degli Studi di Perugia , via Elce di Sotto 8, I-06123 Perugia, Italy.
authors: Francesca
authors: F
authors: Nunzi
authors: Computational Laboratory of Hybrid/Organic Photovoltaics (CLHYO), CNR-ISTM, via Elce di Sotto 8, I-06123 Perugia, Italy.|CompuNet, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy.
authors: Filippo
authors: F
authors: De Angelis
authors: Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States.
authors: Annabella
authors: A
authors: Selloni