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Carrier Dynamics of Dye Sensitized-TiO2 in Contact with Different Cobalt Complexes in the Presence of Tri(p-anisyl)amine Intermediates
Uppsala Univ, Angstrom Lab, Dept Chem, Box 523, SE-75120 Uppsala, Sweden.;Imperial Coll London, Dept Chem, London SW7 2AZ, England..
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Applied Physical Chemistry.
Uppsala Univ, Angstrom Lab, Dept Chem, Box 523, SE-75120 Uppsala, Sweden..
2018 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 122, no 26, p. 14345-14354Article in journal (Refereed) Published
Abstract [en]

Heterogeneous charge transfer processes at sensitized wide bandgap semiconductor surfaces are imperative for both fundamental knowledge and technical applications. Herein, we focus on the investigation of carrier dynamics of a triphenylamine-based dye, LEG4, sensitized TiO2 (LEG4/TiO2) in contact with two types of electrolyte systems: pure cobalt-based electrolytes and in combination with an organic donor, tri(p-anisyl)amine (TPAA). Four different cobalt redox systems with potentials spanning a 0.3 V range were studied, and the carrier recombination and regeneration kinetics were monitored both at low and at high TiO2 (e(-)) densities (1.3 X 10(18) and 1.3 X 10(19) cm(-3), respectively). The results reveal that the introduction of the TPAA intermediate more effectively suppress the recombination loss of TiO2 (e(-)) under high charge conditions, close to open-circuit, as compared to low charge conditions. As a result, the charge transfer from the cobalt complexes to the oxidized dyes is significantly improved by the addition of TPAA. Dye-sensitized solar cells fabricated with the TPAA-containing electrolytes demonstrate remarkable improvement in both V-OC and J(SC) and lead to more than 25% increase of the light-to-electricity conversion efficiency. Furthermore, an unprecedented detrimental impact of TPAA on the device performance was identified when the redox potential of the TPAA donor and the cobalt complexes are close. This is ascribed to the formation of TPAA(center dot+) which can act as an active recombination centers and thus lower the solar cell performance. These insights point at a strategy to enhance the lifetimes of electrons generated in sensitized semiconductor electrodes by overcoming the charge recombination between TiO2 and the oxidized dye under high carrier densities in the semiconductor substrate and offer practical guidance to the design of future efficient electrolyte systems for dye-sensitized solar cells.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018. Vol. 122, no 26, p. 14345-14354
National Category
Chemical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-232616DOI: 10.1021/acs.jpcc.8b03395ISI: 000438178900013Scopus ID: 2-s2.0-85048726885OAI: oai:DiVA.org:kth-232616DiVA, id: diva2:1236076
Funder
Swedish Energy AgencySwedish Research CouncilStiftelsen Olle Engkvist Byggmästare
Note

QC 20180731

Available from: 2018-07-31 Created: 2018-07-31 Last updated: 2018-10-16Bibliographically approved

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Hao, YanKloo, Lars

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