Improved Performance of Solid-State Grätzel Solar Cell by Cosensitization of Quantum Dot and Dye

We report a new cosensitization utilizing quantum dot (QD) PbS and Cis-(SCN)₂Bis(2,2'-bipyridyl-4,4'-dicarboxylate) ruthenium (N3) dye on the nanoporous TiO₂ film. Solid-state Grätzel solar cells with the cosensitized films show an improved overall efficiency by 200% relative to the cells assembled with only N3 sensitization and an extremely high open-circuit voltage of 840 mV, and a fill factor of 70.5%. Back reaction characteristics of the above cells are also investigated, demonstrating a great suppression of recombination due to cosensitization. It seems that the cosensitization also facilitates the electron injection into the conduction band of TiO₂.