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Improving the photoresponse of copper(I) dyes in dye-sensitized solar cells by tuning ancillary and anchoring ligand modules

Bozic-Weber, B. and Brauchli, S. Y. and Constable, E. C. and Fürer, S. O. and Housecroft, C. E. and Malzner, F. J. and Wright, I. A. and Zampese, J. A.. (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.

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Official URL: http://edoc.unibas.ch/dok/A6183859

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Abstract

The syntheses of five homoleptic copper(I) complexes [CuL2][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 [CuL2][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)(Lanchor)]+ 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.
Faculties and Departments:05 Faculty of Science > Departement Chemie > Chemie > Anorganische Chemie (Housecroft)
UniBasel Contributors:Malzner, Frederik and Zampese, Jennifer Ann and Brauchli, Sven and Wright, Iain and Fürer, Sebastian and Malzner, Frederik Jürgen and Constable, Edwin Charles and Housecroft, Catherine Elizabeth and Bozic Weber, Biljana
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:Royal Society of Chemistry
ISSN:1477-9226
e-ISSN:1477-9234
Note:Publication type according to Uni Basel Research Database: Journal article
Identification Number:
Last Modified:03 May 2017 14:14
Deposited On:06 Dec 2013 09:35

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