Sensitization of Nanocrystalline TiO2 with Multibranched Organic Dyes and Co(III)/(II) Mediators: Strategies to Improve Charge Collection Efficiency

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• 作者：Miriam Mba ; Marco D鈥橝cunzo ; Patrizio Salice ; Tommaso Carofiglio ; Michele Maggini ; Stefano Caramori ; Alessandra Campana ; Alessandro Aliprandi ; Roberto Argazzi ; Stefano Carli ; Carlo A. Bignozzi
• 刊名：Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：October 3, 2013
• 年：2013
• 卷：117
• 期：39
• 页码：19885-19896
• 全文大小：683K
• 年卷期：v.117,no.39(October 3, 2013)
• ISSN：1932-7455

文摘

The photoelectrochemical properties of thiophene-triphenylamine (TTPA) sensitizers (TTPA1鈥?) used in association with different cobalt based mediators, including kinetically fast shuttles such as [Co(bpy)₃]^3+/2+ and [Co(phen)₃]^3+/2+ and sterically hindered couples like [Co(dtb)₃]^3+/2+ were studied by combining molecular modeling, spectroscopic, and photoelectrochemical techniques. The results indicate that the presence of multiple anchoring points on the dye structure improves its adsorption stability onto TiO₂ but induces a pseudoplanar adsorption geometry which is not suited to insulate properly the surface of the semiconductor and of the back contact, against electron recombination; particularly when kinetically fast shuttles are employed. This drawback could be successfully countered by exploiting both a compact blocking underlayer and the chemisorption of octyl triethoxysilane (Si鈥揅8) acting as a molecular barrier onto the TiO₂ surface, thus limiting the access of the oxidized mediator to the exposed titania sites. These treatments improve the electron collection efficiency up to 80鈥?0% with the I^{鈥?/sup>/I₃鈥?/sup> couple and up to 70% when the [Co(dtb)₃]3+/2+ mediator was used.}