Photoinduced excitation and charge transfer processes of organic dyes with siloxane anchoring groups: a combined spectroscopic and computational study

Year: 2017

Authors: Castellucci E., Monini M., Bessi M., Iagatti A., Bussotti L., Sinicropi A., Calamante M., Zani L., Basosi R., Reginato G., Mordini A., Foggi P., Di Donato M.

Autors Affiliation: LENS European Lab Nonlinear Spect, Via N Carrara 1, I-50019 Sesto Fiorentino, Italy; CNR, ICCOM, Ist Chim Composti Organometallici, Via Madonna Piano 10, I-50019 Sesto Fiorentino, Italy; Univ Firenze, Dipartimento Chim Ugo Schiff, Via Lastruccia 3-13, I-50019 Sesto Fiorentino, Italy; Univ Siena, Dipartimento Biotecnol Chim & Farm, Via A Moro 2, I-53100 Siena, Italy; Ist Nazl Ottica, Largo Enrico Fermi 6, I-50125 Florence, Italy; CSGI Consorzio Sviluppo Sistemi Grande Interfase, Via Lastruccia 3, I-50019 Sesto Fiorentino, Italy; Univ Perugia, Dipartmento Chim, Via Elce di Sotto 8, I-06123 Perugia, Italy.

Abstract: Dye-sensitized solar cells (DSSCs) have attracted significant interest in the last few years as effective low-cost devices for solar energy conversion. We have analyzed the excited state dynamics of several organic dyes bearing both cyanoacrylic acid and siloxane anchoring groups. The spectroscopic properties of the dyes were studied both in solution and when adsorbed on a TiO2 film using stationary and time-resolved techniques, probing the sub-picosecond to nanosecond time interval. The comparison between the spectra registered in solution and on the solid substrate evidences different pathways for the energy and electron relaxation. The transient spectra of the TiO2-adsorbed dyes show the appearance of a long wavelength excited state absorption band, attributed to the cationic dye species, which is absent in the spectra measured in solution. Furthermore, the kinetic traces of the samples adsorbed on TiO2 film show a long decay component not present in solution which constitutes an indirect evidence of electron transfer between the dye and the semiconductor. The interpretation of the experimental results has been supported by theoretical DFT calculations of the excited state energies and by the analysis of molecular orbitals of the analyzed dye molecules.

Journal/Review: PHYSICAL CHEMISTRY CHEMICAL PHYSICS

Volume: 19      Pages from: 15310  to: 15323

More Information: This project has received funding from the European Union´s Horizon 2020 research and innovation programme under grant agreement no. 654148 Laserlab-Europe. (Short: Laserlab-Europe, H2020 EC-GA 654148). The authors thank Ente Cassa di Risparmio di Firenze (“ENERGYLAB´´ project) for financial support, as well as CINECA and CREA (Colle Val d´Elsa, Italy) for the availability of high performance computing resources.
KeyWords: dye-sensitized solar cells; organic dyes; transient absorption spectroscopy
DOI: 10.1039/c7cp01956d

Citations: 10
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