Are Alkynyl Spacers in Ancillary Ligands in Heteroleptic Bis(diimine)copper(I) Dyes Beneficial for Dye Performance in Dye-Sensitized Solar Cells?

• Published in: Molecules (Basel, Switzerland) Vol. 25; no. 7; p. 1528
• Main Authors: Risi, Guglielmo, Becker, Mariia, Housecroft, Catherine E, Constable, Edwin C
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 27.03.2020; MDPI
• Subjects: 2,2'-Dipyridyl - chemical synthesis; 2,2'-Dipyridyl - chemistry; 2,2′-bipyridine; Absorption spectra; Alkynes - chemistry; alkynyl group; Anchoring; Charge transfer; Coloring Agents - chemistry; Copper; Copper - chemistry; Copper compounds; Dielectric Spectroscopy; dye-sensitized solar cell; Dye-sensitized solar cells; Dyes; Electrochemical impedance spectroscopy; Electrochemistry; Electrodes; Electrolytes; Energy; Fluorine; Fluorine - chemistry; Interfaces; Ligands; phosphonic acid anchor; Phosphonic acids; Phosphorous Acids - chemistry; Photovoltaic cells; Quantum efficiency; Short circuit currents; Short-circuit current; Solar cells; Solar Energy; Spacers; Spectroscopy; Tin Compounds - chemistry; Tin oxides; Titanium dioxide; alkynyl group; copper; 2,2′-bipyridine; phosphonic acid anchor; dye-sensitized solar cell
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules25071528

The syntheses of 4,4'-bis(4-dimethylaminophenyl)-6,6'-dimethyl-2,2'-bipyridine ( ), 4,4'-bis(4-dimethylaminophenylethynyl)-6,6'-dimethyl-2,2'-bipyridine ( ), 4,4'-bis(4-diphenylaminophenyl)-6,6'-dimethyl-2,2'-bipyridine ( ), and 4,4'-bis(4-diphenylaminophenylethynyl)-6,6'-dimethyl-2,2'-bipyridine ( ) are reported along with the preparations and characterisations of their homoleptic copper(I) complexes [CuL ][PF ] (L = - ). 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( )(L )] dyes in which is the anchoring ligand ((6,6'-dimethyl-[2,2'-bipyridine]-4,4'-diyl)bis(4,1-phenylene))bis(phosphonic acid) and L = - have been assembled on fluorine-doped tin oxide (FTO)-TiO 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( )( )] and [Cu( )( )] . The alkynyl spacers are not beneficial, leading to a decrease in the short-circuit current density ( ), confirmed by lower values of EQE . Addition of a co-absorbent ( -decylphosphonic acid) to [Cu( )( )] lead to no significant enhancement of performance for DSCs sensitized with [Cu( )( )] . Electrochemical impedance spectroscopy (EIS) has been used to investigate the interfaces in DSCs; the analysis shows that more favourable electron injection into TiO is observed for sensitizers without the alkynyl spacer and confirms higher values for [Cu( )( )] .