Molybdenum Heteropolyoxometalate Thin Films for Solar Cell Applications

Abstract

Thin films of nanocrystalline Thallium doped Molybdenum heteropolyoxometalate (TlPMA) have been deposited on to glass and fluorine-doped tin oxide (FTO) coated glass substrates from aqueous acidic bath using simple chemical bath deposition technique. The different preparative parameters like concentration of bath, deposition time, bath temperature, pH of the bath have been optimized in order to get good-quality photosensitive thin films of Thallium doped Molybdenum heteropolyoxometalate material. Different techniques have been used to characterize nanocrystalline Thallium doped Molybdenum heteropolyoxometalate thin films annealed at 250°C for 2hours at heating rate 10°C/min. Optical absorption study shows the presence of direct transition with band gap energy 2.15eV. The X-ray diffraction (XRD) analysis of the annealed films showed the material is nanocrystalline in nature with simple cubic spinal structure. Energy-dispersive analysis by X-ray (EDAX) study for the sample deposited at optimized preparative parameters shows that presence of P, Mo, O and Tl in the films without any major impurity. Scanning electron microscopy (SEM) for samples deposited at optimized preparative parameters reveals that spherical grains are uniformly distributed over the surface of the substrate indicates the well-defined growth of nanocrystalline (TlPMA) on thin film. PEC characterization of the films is carried out by studying photo response, spectral response and photovoltaic output characteristics. The fill factor (ff) and power conversion efficiency (η) of the cell are 15.0 and 0.42%, respectively.