Plasmonic and charging effects in dye-sensitized solar cells with Au nanoparticles incorporated into the channels of freestanding TiO₂ nanotube arrays by an electrodeposition method

Au nanoparticles (NPs) were incorporated into the channels of freestanding TiO₂ nanotube arrays (TNTAs) by an electrodeposition method and then applied to dye-sensitized solar cells (DSSCs) for light harvesting to improve the power conversion efficiency (PCE). The average size of Au NPs incorporated into TNTA channels was approximately 70 nm, and the extinction of the Au NPs by UV–vis spectra was approximately 530 nm, which is similar to the absorbance of the ruthenium dye (N719) used in DSSCs. The PCE of DSSCs based on TNTAs containing Au NPs increased to 6.80% from a PCE of 5.66% without Au NPs, an enhancement of 20.14% owing to light harvesting from the NP plasmonic and charging effects. However, the PCE of DSSCs based on TNTAs with excess Au NPs decreased from 6.80% to 5.49% due to aggregation of the Au NPs, which led to a decreased open-circuit voltage and fill factor.