“…Additionally, the bandgap (E g ) of CZS can be calculated by the formula (ahn) = A(hn À E g ) 1/2 (where A, a, n, and h represent a constant, absorption coefficient, optical frequency, and Planck's constant, respectively). 60,61 Therefore, the E g of CZS can be estimated to be 2.32 eV from the plots of (ahn) 2 versus (hn) (Fig. 5b).…”