Effect of Ag doping on structural, optical, complex impedance and photovoltaic properties of SnO2 nanoparticles prepared by co-precipitation method for dye sensitized solar cell application

Abstract

The pure SnO2 and Ag-doped snO2 nanoparticles (NPs) were prepared by co-precipitation method. The structural, electrical and optical properties of the material were systematically studied. The XRD patterns of both samples reveal that the presence of cassiterite tetragonal structure and GSAS fittings confirms the incorporation of Ag in SnO2 lattices. The SEM-EDS analysis reveals that the presence of spherical-shaped NPs with the expected elements. The Raman spectra of Ag-doped SnO2 NPs show that the two extra local disorder vibrational modes while comparing with pure SnO2. The UV-Vis spectroscopy result shows that the Ag doping reduces the optical band gap and increases Urbach tail energy with a reduced effective energy band gap in Ag-doped SnO2 NPs. The Photoluminescence spectrum confirms the presence of the defects like oxygen vacancies; however, these defects are increased by the Ag-doped SnO2 system. From the dielectric measurements, the conductivity of both samples followed Jonscher’s power law. The nonlinear least-square fittings on Nyquist plots of both samples suggested that the conduction process took place predominantly through grain boundary in SnO2 NPs whereas through grains in Ag-SnO2 NPs. This nature of band gap narrowing with increased conductivity in Ag-doped samples drives these samples for good solar cell activity applications. As expected, photovoltaic measurements show higher power conversion efficiency in Ag-doped SnO2 NPs. These results were discussed by correlating optical and dielectric properties of SnO2 and Ag-doped SnO2 NPs which gave a broad understanding for device fabrications successfully.