“…The Raman spectra presented in Fig. 2 (b) reveal two distinct peaks for all samples attributed to A1 and A2 vibration modes: one at 283.31 cm −1 (found for 150 0 C-ST and RT-TB films), 285.24 cm −1 (150 0 C-TB) and 287.17 cm −1 (RT-ST) which arises from the vibration of Cu atoms in the CZTS crystal structure (known to appear around 287 cm −1 ) [ 23 , 24 ], and the others at 327.67 cm −1 (150 0 C-TB), 329.60 cm −1 (RT-ST), 333.45 cm −1 (150 0 C-ST) and 335.38 cm −1 (RT-TB), related to the presence of Cu, Zn, and Sn in the CZTS film [ 16 , 24 ].…”