Syntheses, characterization, crystal structures and applications as sensitizers in solar cells of novel heteroleptic Cu(I) complexes containing nitrile-substituted 2,2'-bipyridyl ligands.

Two novel Cu(I) tetradentate heteroleptic complexes, including nitrile-substituted bipyridines that can be anchored to semiconductor surfaces to be assembled in DSSCs, were synthesized and characterized by spectroscopic and electrochemical techniques. The crystal structures of both species were determined by X-ray diffraction. Results from DFT and TD-DFT calculations were found to be consistent with the experimental data. Emission at room temperature was observed for both complexes in the solid state, making them promising alternatives for the development of light-emitting diodes. We report for the first time the experimental evidence of photovoltaic conversion devices formed by Cu(I) complexes anchored to a TiO2 surface by means of nitrile groups present in substituted bipyridines, and subsequently tested as sensitizers for DSSCs, obtaining efficiency values for light to electrical energy conversion similar to those previously reported for analogous complexes with anchoring carboxylic groups.

Heteroleptic Ruthenium(II) Complexes with 2,2'-Bipyridines Having Carbonitriles as Anchoring Groups for ZnO Surfaces: Syntheses, Physicochemical Properties, and Applications in Organic Solar Cells.

Heteroleptic ruthenium (II) complexes were used for sensitizing ZnO surfaces in organic solar cells (OSCs) as mediators with photoactive layers. The complexes [Ru(4,4'-X2-bpy)(Mebpy-CN)2]2+ (with X = -CH3, -OCH3 and -N(CH3)2; bpy = 2,2'-bipyridine; Mebpy-CN = 4-methyl-2,2'-bipyridine-4'-carbonitrile) were synthesized and studied by analytical and spectroscopical techniques. Spectroscopic, photophysical, and electrochemical properties were tuned by changing the electron-donating ability of the -X substituents at the 4,4'-positions of the bpy ring and rationalized by quantum mechanical calculations. These complexes were attached through nitrile groups to ZnO as interfacial layer in an OSC device with a PBDB-T:ITIC photoactive layer. This modified inorganic electron transport layer generates enhancement in photoconversion of the solar cells, reaching up to a 23% increase with respect to the unsensitized OSCs. The introduction of these dyes suppresses some degradative reactions of the nonfullerene acceptor due to the photocatalytic activity of zinc oxide, which was maintained stable for about 11 months. Improving OSC efficiencies and stabilities can thus be achieved by a judicious combination of new inorganic and organic materials.

Novel Heteroleptic Ruthenium(II) Complexes with 2,2'- Bipyridines Containing a Series of Electron-Donor and Electron-Acceptor Substituents in 4,4'-Positions: Syntheses, Characterization, and Application as Sensitizers for ZnO Nanowire-Based Solar Cells.

A novel series of complexes of the formula [Ru(4,4'-X2-bpy)2(Mebpy-CN)](PF6)2 (X = -CH3, -OCH3, -N(CH3)2; Mebpy-CN = 4-methyl-2,2'-bipyridine-4'-carbonitrile) have been synthesized and characterized by spectroscopic, electrochemical, and photophysical techniques. Inclusion of the electron-withdrawing substituent -CN at one bpy ligand and different electron-donor groups -X at the 4,4'-positions of the other two bpy ligands produce a fine tuning of physicochemical properties. Redox potentials, electronic absorption maxima, and emission maxima correlate well with Hammett's σp parameters of X. Quantum mechanical calculations are consistent with experimental data. All the complexes can be anchored through the nitrile moiety of Mebpy-CN over ZnO nanowires in dye-sensitized solar cells that exhibit an improvement of light to electrical energy conversion efficiency as the electronic asymmetry increases in the series.