To deprotect or not to deprotect: Phosphonate ester versus phosphonic acid anchor ligands in copper(I)-based dye-sensitized solar cells

The performances of n-type DSCs containing the heteroleptic copper(I) dyes [Cu(1)(dmbpy)]+ and [Cu(2)(dmbpy)]+ (1 = ((6,6′-dimethyl-[2,2′-bipyridine]-4,4′-diyl)bis(4,1-phenylene))bis(phosphonic acid); 2 = tetraethyl ((6,6′-dimethyl-[2,2′-bipyridine]-4,4′-diyl)bis(4,1-phenylene))bis(phosphonate); dmbpy = 6,6′-dimethyl-2,2′-bipyridine) have been evaluated to determine whether or not deprotection of the phosphonate ester prior to assembly of the heteroleptic [Cu(Lanchor)(Lancillary)]+ dye is an essential step. Fully masked DSCs containing [Cu(1)(dmbpy)]+ with I3−/I− electrolyte show conversion efficiencies, η, of ≈2.1% compared to ≈0.3% for those containing [Cu(2)(dmbpy)]+ in which 2 may be partially deprotected in situ. Compound 2 is a surprisingly effective ancillary ligand; DSCs containing [Cu(1)(2)]+ exhibit η ≈2%. EQE spectra for DSCs containing the dyes [Cu(1)(dmbpy)]+ and [Cu(1)(2)]+ are similar, showing broad bands with λmax around 460–480 nm and EQEmax = 40%.

The performances of n-type DSCs containing heteroleptic copper(I) dyes with phosphonic acid or corresponding phosphonate ester as anchoring ligand have been evaluated to determine whether deprotection of the ester prior to assembly of the adsorbed dye is a prerequisite.Figure optionsDownload as PowerPoint slide