“…[ 19,39 ] In both the samples, the Raman spectra (≈532 nm excitation laser) (Figure 3b) show peaks at 286 and 337 cm −1 , while spectra with ≈633 nm excitation wavelength (Figure 3c) show peaks at 264, 286, 304, 337, and 367 cm −1 corresponding to the kesterite phase. [ 19,39,40 ] The Raman shifts observed at 264, 286, 304, and 337 cm −1 belong to the A symmetry mode whereas the peak at 367 cm −1 corresponds to the B symmetry mode of the kesterite phase. [ 19,39,40 ] Since Cu 2 ZnSiS 4 and Cu 2 ZnSnS 4 phases show identical Raman shifts at 264, 286, 304, and 337 cm −1 , Cu 2 ZnSn x Si 1− x S 4 phase could not be distinguished from CZTS.…”