Plasmon Effect of Silver Nanoparticles on the Sensitization of Titanium Dioxide Nanorods with N719 Dye
Abstract
The plasmon effect of Ag nanoparticles (NPs) on the sensitization of TiO2 nanorods (NRs) with ruthenium dye N719 was studied. TiO2 NRs were prepared by hydrothermal method. SEM analysis revealed that the synthesis resulted in the formation of TiO2 NRs with a length of ~2.6 µm and a diameter of 55 – 65 nm. The diameter of the deposited Ag NPs ranges from 5 to 12 nm. Measurements of the kinetics of fluorescence and long-lived luminescence of the dye showed that the lifetime of both types of N719 luminescence is reduced by ~2.2 times in the presence of semiconductor. At the same time, along with the dye fluorescence (near the 535 nm), a broad luminescence band at 720 nm was recorded, corresponding to the recombination luminescence of TiO2. The results obtained indicate the electron transfer from both singlet- and triplet-excited dye molecules to TiO2. The charge transfer efficiency was also evaluated from photovoltaic measurements of dye-sensitized solar cells (DSSC) based on TiO2 NRs with different concentrations of Ag NPs. The best photovoltaic parameters were registered for the sample of TiO2 NRs with Ag NPs, obtained from 1.5 mmol of AgNO3. In these samples the efficiency of the solar cell was increased by 3.2 times ompared to the sample without Ag NPs. The increase in efficiency is associated with the improvement of charge transport characteristics of solar cells with Ag NPs, which was confirmed by impedance measurements. The injection of hot electrons from Ag NPs into the TiO2 conduction band is also possible, which contributes to the enhancement of solar cell efficiency. The obtained data demonstrate the potential of using of plasmon effect of metal NPs to enhance the efficiency of DSSCs and could be applied in the design of high-performance photovoltaic systems.