Structural, optical, electrical and photovoltaic electrochemical characterization of spray deposited NiWO4 thin films

The preparation of nickel tungstate (NiWO4) thin film by spray pyrolysis (SP) with ammonical solution is presented. The phase and surface morphology characterizations have been carried out by X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis, respectively. The study of optical absorption spectrum in the wavelength range 350–850 nm shows the presence of direct as well as indirect band gaps in the material, respectively found to be 2.28 and 2.00 eV. The thin film material shows semiconducting behaviour and highly resistive at room temperature as evident from its dc electrical conductivity measurements obtained by the Two Point Probe method in the temperature range 310–500 K. The thin films deposited on fluorine doped tin oxide (FTO) coated conducting glass substrates are used as photoanode in photovoltaic electrochemical (PVEC) cell. The PVEC cell configuration is: NiWO4|Ce4+, Ce3+|Pt; 0.1 M in 0.1N H2SO4. The PVEC characterization reveals the fill factor and power conversion efficiency to be 0.47 and 0.78%, respectively. The flat band potential is found to be −0.32 V (SCE).