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Title: Improving the photoresponse of copper(i) dyes in dye-sensitized solar cells by tuning ancillary and anchoring ligand modules
Authors: Bozic-Weber, Biljana
Brauchli, Sven Y.
Constable, Edwin C.
Furer, Sebastian O.
Housecroft, Catherine E.
Malzner, Frederik J.
Wright, Iain A.
Zampese, Jennifer A.
Issue Date: 2013
Publisher: © The Royal Society of Chemistry
Citation: BOZIC-WEBER, B., 2013. Improving the photoresponse of copper(i) dyes in dye-sensitized solar cells by tuning ancillary and anchoring ligand modules. Dalton Transactions, 42(34), pp. 12293-12308.
Abstract: The syntheses of five homoleptic copper(i) complexes [CuL 2][PF6] are described in which L is a 4,4′-di(4- bromophenyl)-6,6′-dialkyl-2,2′-bipyridine ligand (compounds 1-4 with methyl, nbutyl, isobutyl and hexyl substituents, respectively) or 4,4′-di(4-bromophenyl)-6,6′-diphenyl-2,2′- bipyridine (5). The new ligands 2-5 and copper(i) complexes [CuL 2][PF6] (L = 1-5) have been fully characterized. The single crystal structures of 2{[Cu(1)2][PF6]} ·3Me2CO, [Cu(2)2][PF6], 2{[Cu(3) 2][PF6]}·Et2O and [Cu(5) 2][PF6]·CH2Cl2 have been determined. The first three structures show similar distorted tetrahedral environments for the Cu+ ions with angles between the least squares planes of the bpy domains of 85.6, 86.4 and 82.9°, respectively; in contrast, the Cu+ ion in [Cu(5)2][PF6] ·CH2Cl2 is in a flattened coordinate environment due to intra-cation face-to-face π-interactions. The solution absorption spectra of the complexes with ligands 1-4 are virtually identical with an MLCT band with values of λmax = 481-488 nm. In contrast, the absorption spectrum of [Cu(5)2][PF6] shows two broad bands in the visible region. Cyclic voltammetric data show that oxidation of the copper(i) centre occurs at a more positive potential in [Cu(2) 2][PF6], [Cu(3)2][PF6] and [Cu(4)2][PF6] than in [Cu(1)2][PF6] or [Cu(5)2][PF6] with the latter being oxidized at the lowest potential. The complexes have been used to prepare dye-sensitized solar cells (DSCs) incorporating heteroleptic dyes of type [Cu(L)(L anchor)]+ where L is 1-5 and Lanchor is a 6,6′-dimethyl-2,2′-bipyridine functionalized in the 4- and 4′-positions with phosphonic acid groups with (Lanchor = 7) and without (Lanchor = 6) a spacer between the metal-binding and anchoring domains. The presence of the spacer results in enhanced performances of the dyes, and the highest energy conversion efficiencies are observed for the dyes [Cu(3)(7)]+ (η = 2.43% compared to 5.96% for standard dye N719) and [Cu(5)(7)]+ (η = 2.89% compared to 5.96% for N719). Measurements taken periodically over the course of a week indicate that the cells undergo a ripening process (most clearly seen for [Cu(5)(6)]+ and [Cu(5)(7)]+) before their optimum performances are achieved. IPCE (EQE) data are presented and confirm that, although the photo-to-current conversions are promising (37-49% for λmax ≈ 480 nm), the copper(i) dyes do not realize the broad spectral response exhibited by N719. © 2013 The Royal Society of Chemistry.
Description: This is an Open Access Article. It is published by Royal Society of Chemistry under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND). Full details of this licence are available at: http://creativecommons.org/licenses/by-nc-nd/4.0/
Sponsor: We thank the European Research Council (Advanced Grant 267816 LiLo), the Swiss National Science Foundation, the Swiss Nanoscience Institute and the University of Basel for financial support.
Version: Published
DOI: 10.1039/c3dt51416a
URI: https://dspace.lboro.ac.uk/2134/25424
Publisher Link: http://dx.doi.org/10.1039/c3dt51416a
ISSN: 1477-9226
Appears in Collections:Published Articles (Chemistry)

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