Inhibition of charge transfer and recombination processes in CdS/N719 co-sensitized solar cell with high conversion efficiency

In the hybrid structure employing CdS/N719 QD/dye co-sensitized photoelectrode, it is revealed by consistent results from the steady-state and time-resolved photoluminescence (PL) that the QD regeneration was realized by the effective charge transfer from the dye sensitizer, resulting in a significant PL quenching. This is helpful for retarding the recombination in the device. Furthermore, by varying the thickness of the TiO2 film, the light harvesting efficiency and the charge collection efficiency were balanced, leading to an optimal TiO2 thickness of 22 μm and a power conversion efficiency (PCE) of about 6.5%. Compared with the dye N719 only sensitized system with the same dye loading(with an efficiency of 5.09%), the co-sensitization of dye N719 and CdS (with an efficiency of 6.44%) enhanced the overall PCE significantly by 26.5% Notably, this is one of the best reported efficiencies for the QD-dye co-sensitized solar cells.