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 Laboratory for Non-Linear Spectroscopy), Via N. Carrara 1, 50019 Sesto Fiorentino, Italy; Istituto di Chimica dei Composti Organometallici (CNR-ICCOM), Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy; Dipartimento di Chimica ‘Ugo Schiff’, Università di Firenze, via della Lastruccia 3-13, 50019 Sesto Fiorentino, Italy; Dipartimento di Biotecnologie, Chimica e Farmacia, Università di Siena, Via A. Moro 2, 53100 Siena, Italy; INO, Istituto Nazionale di Ottica Largo Enrico Fermi 6, I-50125 Florence, Italy; Dipartmento di Chimica, Università degli studi di Perugia, via Elce di Sotto 8, 06123 Perugia, Italy; CSGI, Consorzio per lo Sviluppo dei Sistemi a Grande Interfase, via della Lastruccia 3, 50019, Sesto Fiorentino, 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.


Volume: 19      Pages from: 15310  to: 15323

KeyWords: dye-sensitized solar cells; organic dyes; transient absorption spectroscopy
DOI: 10.1039/c7cp01956d

Citations: 10
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