“…Furthermore, using the widely used Tauc's approach, 55,56 the optical band gaps of all the synthesised compounds, 13a–j , were determined from the absorption spectra. It is centred on the Tauc–Davis–Mott equation (eqn (1)), which explains the relation between the band gap E g and the absorption coefficient ( α ).( αhν ) n = A ( hν − E g )where hν is the energy of the incident photon, A is the proportionality constant, and n is the coefficient that depends on the kind of electronic transition.…”