DOPING EFFECTS OF TRANSITION-METAL IONS ON THE PHOTOSENSITIZATION OF WO3 PARTICLES

Diffuse reflection spectra of WO3 powders doped with first row transition metal ions Ti(III), V(IV), Cr(III), Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) and RuO2 indicate that the doping has increased the absorbance of the doped semiconductor in the visible region of the solar radiation. The fundamental band gap of all the doped WO3 is being shifted towards the longer wavelength region. Doping also changes the colour of the WO3 powder. RuO2, Cr(III), Mn(II) and Fe(III) are found to be more effective in photosensitization. The spectral observations have been correlated with the crystal field transitions of the metal ions. X-ray diffraction studies of the doped and undoped WO3 powders proved that there is no modification in the crystal structure of WO3 due to doping. These studies are found to be helpful in selecting the dopants to sensitize the semiconductor powders.