| Summary: | The syntheses of 4,4′-bis(4-dimethylaminophenyl)-6,6′-dimethyl-2,2′-bipyridine (<b>1</b>), 4,4′-bis(4-dimethylaminophenylethynyl)-6,6′-dimethyl-2,2′-bipyridine (<b>2</b>), 4,4′-bis(4-diphenylaminophenyl)-6,6′-dimethyl-2,2′-bipyridine (<b>3</b>), and 4,4′-bis(4-diphenylaminophenylethynyl)-6,6′-dimethyl-2,2′-bipyridine (<b>4</b>) are reported along with the preparations and characterisations of their homoleptic copper(I) complexes [CuL<sub>2</sub>][PF<sub>6</sub>] (L = <b>1</b>–<b>4</b>). The solution absorption spectra of the complexes exhibit ligand-centred absorptions in addition to absorptions in the visible region assigned to a combination of intra-ligand and metal-to-ligand charge-transfer. Heteroleptic [Cu(<b>5</b>)(L<sub>ancillary</sub>)]<sup>+</sup> dyes in which <b>5</b> is the anchoring ligand ((6,6′-dimethyl-[2,2′-bipyridine]-4,4′-diyl)bis(4,1-phenylene))bis(phosphonic acid) and L<sub>ancillary</sub> = <b>1</b>–<b>4</b> have been assembled on fluorine-doped tin oxide (FTO)-TiO<sub>2</sub> electrodes in dye-sensitized solar cells (DSCs). Performance parameters and external quantum efficiency (EQE) spectra of the DSCs (four fully-masked cells for each dye) reveal that the best performing dyes are [Cu(<b>5</b>)(<b>1</b>)]<sup>+</sup> and [Cu(<b>5</b>)(<b>3</b>)]<sup>+</sup>. The alkynyl spacers are not beneficial, leading to a decrease in the short-circuit current density (<i>J</i><sub>SC</sub>), confirmed by lower values of EQE<sub>max</sub>. Addition of a co-absorbent (<i>n</i>-decylphosphonic acid) to [Cu(<b>5</b>)(<b>1</b>)]<sup>+</sup> lead to no significant enhancement of performance for DSCs sensitized with [Cu(<b>5</b>)(<b>1</b>)]<sup>+</sup>. Electrochemical impedance spectroscopy (EIS) has been used to investigate the interfaces in DSCs; the analysis shows that more favourable electron injection into TiO<sub>2</sub> is observed for sensitizers without the alkynyl spacer and confirms higher <i>J</i><sub>SC</sub> values for [Cu(<b>5</b>)(<b>1</b>)]<sup>+</sup>.
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