High Stability Tetradentate Ligand Copper Complexes and Organic Small Molecule Hybrid Electrolyte for Dye-Sensitized Solar Cells

A novel copper complex (CuL), where L is the tetradentate ligand 6,6-bis(pyridine-2-methoxy) methyl-2,2-pyridine, was designed and applied in dyesensitized solar cells as a redox couple. Cyclic voltammetry demonstrates that the tetradentate ligand prompt CuL has excellent stability and that a ligand exchange reaction does not occur even in the presence of a high concentration of 4-tertbutylpyridine, although ligand exchange reactions occur frequently with copper complexes containing bidentate ligands. Collision-induced dissociation mass spectrometry measures the collision voltage for the dissociation of the complexes, which is higher than for the traditional copper redox couple, indicating that these complexes have better stability than the traditional copper electrolytes have. Electrochemical impedance and open-circuit voltage delay indicate that the alkoxy chain of the ligand has excellent ability to inhibit photoelectron recombination, greatly prolonging the electron lifetime. The device based on this electrolyte achieved a shortcircuit current density of 14.4 mA cm-2 and a photoelectric conversion efficiency of 9.1%. The hybrid electrolyte was obtained after being combined with organic small molecule TPAA; both Voc and Jsc of the device are improved, resulting in a 10.0 % PCE for the device and maintained an initial efficiency of 96% after 700 hours.