Issue 7, 2016

Combining phosphonic acid-functionalized anchoring ligands with asymmetric ancillary ligands in bis(diimine)copper(i) dyes for dye-sensitized solar cells

Abstract

A ‘surfaces-as-ligands’ strategy is used to assemble heteroleptic copper(I) dyes [Cu(Lanchor)(Lancillary)]+ on FTO/TiO2 electrodes for dye-sensitized solar cells (DSCs). The anchoring domain, Lanchor, is either ((6,6′-diphenyl-[2,2′-bipyridine]-4,4′-diyl)bis(4,1-phenylene))bis(phosphonic acid) (1) or ((6,6′-dimethyl-[2,2′-bipyridine]-4,4′-diyl)bis(4,1-phenylene))bis(phosphonic acid) (2). Asymmetric ancillary ligands with a 2,2′-bipyridine metal-binding domain are used to counter the sterically-demanding 6,6′-diphenyl-substitution pattern in anchor 1; Lancillary = 6-methyl-4-phenyl-2,2′-bipyridine (3), 6-methyl-4-(4-bromophenyl)-2,2′-bipyridine (4), 6-methyl-4-(4-methoxyphenyl)-2,2′-bipyridine (5) or 6-methyl-4-(3,4,5-trimethoxyphenyl)-2,2′-bipyridine (6). Solid-state absorption spectra of adsorbed [Cu(1)(Lancillary)]+ and [Cu(2)(Lancillary)]+, and external quantum efficiency (EQE) spectra of DSCs containing these dyes confirm that incorporation of 6,6′-diphenyl-substituted 1 leads to a broadened spectral response at lower energies compared to dyes with anchor 2; dye-loading is higher for [Cu(2)(Lancillary)]+ than for [Cu(1)(Lancillary)]+, and EQEmax is >41% for [Cu(2)(Lancillary)]+ compared to <12% for [Cu(1)(Lancillary)]+. Enhanced values of the short-circuit current density (JSC) are observed on going from anchor 1 to 2, independent of Lancillary. For the series of [Cu(2)(Lancillary)]+ dyes, photoconversion efficiencies (confirmed using four DSCs per dye) vary with Lancillary in the order 35 > 6 > 4 on the day of DSC assembly, and 5 > 36 > 4 after a week. The best performing DSCs achieve efficiencies of ∼37% relative to N719 set at 100%.

Graphical abstract: Combining phosphonic acid-functionalized anchoring ligands with asymmetric ancillary ligands in bis(diimine)copper(i) dyes for dye-sensitized solar cells

Supplementary files

Article information

Article type
Paper
Submitted
30 11 2015
Accepted
23 12 2015
First published
12 1 2016
This article is Open Access
Creative Commons BY license

RSC Adv., 2016,6, 5205-5213

Author version available

Combining phosphonic acid-functionalized anchoring ligands with asymmetric ancillary ligands in bis(diimine)copper(I) dyes for dye-sensitized solar cells

A. Büttner, S. Y. Brauchli, R. Vogt, E. C. Constable and C. E. Housecroft, RSC Adv., 2016, 6, 5205 DOI: 10.1039/C5RA25447G

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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