A new method (named as DASF: Derivation of
absorption spectrum fitting) is proposed for the determination
of optical band gap and the nature of optical transitions
in semiconductors; this method only requires the
measurement of the absorbance spectrum of the sample,
avoiding any needs to film thickness or any other parameters.
In this approach, starting from absorption spectrum
fitting (ASF) procedure and by the first derivation of the
absorbance spectrum, the optical band gap and then the
type of optical transition can be determined without any
presumption about the nature of transition. DASF method
was employed on (60−x)V2O5–40TeO2–xAg2O glassy
systems (hereafter named as TVAgx), in order to confirm
the validity of this new method. For the present glasses,
the DASF results were compared with the results of ASF
procedure for, confirming a very good agreement between
these approaches. These glasses were prepared by using
the melt quenching and blowing methods to obtain bulk
and film samples, respectively. Results show that the optical
band gap variation for TVAgx glasses can be divided
into two regions, 0 ≤ x ≤ 20 and 20 ≤ x ≤ 40 mol%. The
optical band gap has a maximum value equal to 2.72 eV
for x = 40 and the minimum value equal to 2.19 eV for
x = 40. Also, some physical quantities such as the width
of the band tails (Urbach energy), glass density, molar volume,
and optical basicity were reported for the under studied
glasses.