Investigation on optical properties of the ternary TeO2-V2O5-MxOy (NiO and K2O) glassy glasses, effect of MxOy content on the optical band gap and tailing states

Two series of bulk glasses, with composition of 40TeO2– (60 - x)V2O5–xNiO with 0 ≤x ≤ 30 and 50TeO2– (50 - y)V2O5–yK2O with 0 ≤y ≤ 20 (in mol%) have been prepared using the press-melt quenching method. The optical absorption spectra of the glasses have been recorded in the wavelength range 400–800 nm. The fundamental absorption edge has been identified from the optical absorption spectra. The optical band gap and width of the tail of the localized states have been evaluated using available theories. Results show that the values of optical band gap, Eg, decrease from 2.02 to 1.64 eV as the contribution of NiO increases in tellurite-vanadate glasses. While with addition of K2O, an increase in Eg is observed from 1.91 to 2.33 eV. Based on the results, sample with 30% NiO is realized as a promising future device in solar-cell industry.