Donor Effect on the Photoinduced Interfacial Charge Transfer Dynamics of D−π–A Diketopyrrolopyrrole Dye Sensitizers Adsorbed on Titanium Dioxide

In this report, we investigate the effects of a strong electron-donating group on the electron injection and recombination processes of diketopyrrolopyrrole (DPP)-sensitized TiO2 films by comparing the dynamics of triphenylamine donor-installed DPP_A and donor-absent DPP_R dyes. We show that the electron-donating group enhances the intramolecular charge transfer (ICT) characteristics of DPP_A, as demonstrated by a significant spectral redshift in the steady-state measurement of DPP_A compared to that of DPP_R. By comparing the ultrafast transient behaviors of the dye-coated films through femtosecond transient absorption (fs-TA) measurements, we provide insight into the high efficiency of DPP_A: most of the electrons from DPP_A are injected into the conduction band of TiO2 within the time resolution of TA (

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Heewon Bahng, Ulf Anders Hagfeldt, Jacques-Edouard Moser
2018
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https://infoscience.epfl.ch/record/256708?ln=fr

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Femtosecond X-ray absorption study of electron localization in photoexcited anatase TiO2

Edoardo Baldini, Paul Beaud, Camelia Borca, Majed Chergui, Jochen Rittmann, Fabio Giacomo Santomauro, Mahsa Silatani, Patric Zimmermann

Transition metal oxides are among the most promising solar materials, whose properties rely on the generation, transport and trapping of charge carriers (electrons and holes). Identifying the latter's dynamics at room temperature requires tools that combine elemental and structural sensitivity, with the atomic scale resolution of time (femtoseconds, fs). Here, we use fs Ti K-edge X-ray absorption spectroscopy (XAS) upon 3.49 eV (355 nm) excitation of aqueous colloidal anatase titanium dioxide nanoparticles to probe the trapping dynamics of photogenerated electrons. We find that their localization at Titanium atoms occurs in < 300 fs, forming Ti3+ centres, in or near the unit cell where the electron is created. We conclude that electron localization is due to its trapping at pentacoordinated sites, mostly present in the surface shell region. The present demonstration of fs hard X-ray absorption capabilities opens the way to a detailed description of the charge carrier dynamics in transition metal oxides.

Nature Publishing Group2015

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Mesure physique

La mesure physique est l'action de déterminer la ou les valeurs d'une grandeur (longueur, capacité), par comparaison avec une grandeur constante de même espèce prise comme terme de référence (étalon

Electron donor

In chemistry, an electron donor is a chemical entity that donates electrons to another compound. It is a reducing agent that, by virtue of its donating electrons, is itself oxidized in the process.

Dioxyde de titane

Le dioxyde de titane ou oxyde de titane (IV) est un composé d'oxygène et de titane de formule présent dans la nature et fabriqué industriellement. C'est le pigment blanc PW6 du Colour Index, large