Syntheses, physicochemical characterizations, crystal structures and quantum-mechanical calculations of novel heteroleptic Cu(I) complexes with applications in dye-sensitized solar cells

Abstract

We herein report the syntheses, physicochemical characterizations, crystal structures and quantum-mechanical calculations of two new heteroleptic Cu(I) complexes with 1,3-bis(diphenylphosphino)propane (dppp) as a stabilizing ancillary ligand and 4-cyano-4′-methyl-2,2′-bipyridine (Mebpy-CN) or 4,4′-dicyano-2,2′-bipyridine (bpy-(CN)2) as anchoring ligands to semiconductor surfaces. The theoretical calculations support the experimental structural results and the obtained visible absorption data with their assignments. We also describe their chemical links to FTO/TiO2 electrodes (FTO = fluoride-doped tin oxide) and their electrical impedance properties, that disclose an improvement in the efficiency of the charge transfer process of the sensitized electrodes with respect to the bare ones. A good fit can be obtained when using an equivalent circuit previously reported for Ru complexes with analogous groups anchored to TiO2. These sensitized electrodes were used to assemble new Dye-Sensitized Solar Cells (DSSCs) with solar-to-electrical energy conversion efficiencies considerably higherthan those reported for cells with analogous Cu complexes attached to TiO2 surfaces.