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Title: Dye-sensitized solar cells with hole-stabilizing surfaces: "inorganic" versus "organic" strategies
Authors: Hostettler, Nik
Wright, Iain A.
Bozic-Weber, Biljana
Constable, Edwin C.
Housecroft, Catherine E.
Issue Date: 2015
Publisher: © The Authors. Published by the Royal Society of Chemistry.
Citation: HOSTETTLER, N. ...et al., 2015. Dye-sensitized solar cells with hole-stabilizing surfaces: "inorganic" versus "organic" strategies. RSC Advances, 5(47), pp. 37906-37915.
Abstract: © The Royal Society of Chemistry 2015.Two 2,2′:6′,2′′-terpyridine ligands (9 and 10) incorporating second-generation diphenylamino-dendrons have been synthesized and characterized; one ligand contains chromophoric benzothiadiazole domains. Using the 'surface-as-ligand, surface-as-complex' strategy, zinc(ii)-containing sensitizers [Zn(L<inf>anchor</inf>)(L<inf>ancillary</inf>)]<sup>2+</sup> with carboxylic or phosphonic acid anchors (1 and 2, respectively) have been assembled and tested in n-type DSCs. The solid-state absorption spectra of dye-functionalized electrodes show a broad spectral response for all the dyes with enhanced intensity for those containing the benzothiadiazole units. However, the [Zn(L<inf>anchor</inf>)(L<inf>ancillary</inf>)]<sup>2+</sup> dyes perform poorly, exhibiting very low values of the short-circuit current density (J<inf>SC</inf>) and open-circuit voltage (V<inf>OC</inf>). The external quantum efficiency (EQE) spectra confirm that electron injection occurs, but EQE<inf>max</inf> is ≤3%. Non-optimal positioning of the thiadiazole domain in the dye probably contributes to the poor performances. Screening of DSCs containing FTO/TiO<inf>2</inf> photoanodes without adsorbed dye shows that they generate small short-circuit current densities and open-circuit voltages which contribute significantly to parameters reported for badly performing dyes. An organic dye 11, structurally similar to 10 and containing a 2-cyanoacrylic acid anchor, is also reported. This exhibits a broad and intense spectral response between 300 and 600 nm, and shows efficient electron injection over a broad wavelength range. DSCs containing 11 are stable over a 17 day period and show global efficiencies of 3.93-4.57% (ca. 70% with respect to N719 set at 100%). Ground state DFT calculations reveal that the HOMO in each of [Zn(1)(9)]<sup>2+</sup>, [Zn(2)(9)]<sup>2+</sup>, [Zn(1)(10)]<sup>2+</sup>, [Zn(2)(10)]<sup>2+</sup> and 11 is localized on the peripheral diphenylamino units, allowing for hole-transfer to the reduced electrolyte. In 11, a major contribution from the 2-cyanoacrylic acid anchoring group appears in the LUMO manifold; however, while the LUMO in each zinc(ii) dye is localized on anchoring ligand 1 or 2, it is concentrated close to the metal centre which may contribute to poor electron injection.
Description: This is an Open Access Article. It is published by Royal Society of Chemistry under the Creative Commons Attribution 3.0 Unported Licence (CC BY). Full details of this licence are available at: http://creativecommons.org/licenses/by/3.0/
Version: Published
DOI: 10.1039/c5ra05630f
URI: https://dspace.lboro.ac.uk/2134/23506
Publisher Link: http://dx.doi.org/10.1039/c5ra05630f
Appears in Collections:Published Articles (Chemistry)

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