“…UV-vis absorption spectra measurements were performed in a Unicam 8700 spectrometer system over the 190-900 nm wavelength range. Energy band gap (E g ) measurements were carried out by means of optical absorption spectra by using the Tauc's formula for amorphous semiconductors: (ahn)p(hnÀE g ) m [10][11][12][13][14][15][16][17][18][19][20][21], where a is the absorption coefficient, h is the Planck's constant, n is the frequency of the light, and the exponent m takes the values 1 2 and 2 for allowed direct and indirect transitions [10][11][12][13][14][15][16][17][18][19][20][21]. Actually, as the absorption coefficient is proportional to the optical density (O.D.…”