The evolution of the crystallinity depending on the annealing temperature in the CTS films obtained by spray pyrolysis

We report the effect of temperature annealing with nitrogen atmosphere in the CTS film deposited by spray pyrolysis, and their evolution in crystallinity, as well as the contribution in the optical parameters, such as optical absorption coefficient, band gap, and the contribution in morphology. We could obtain the Cu₄Sn₇S₁₆ and Cu₂SnS₃ proving with the XRD diffractograms and Raman analysis. The films showed a good crystallinity, and crystallite size between 11.9 nm and 18.1 nm. The optical absorption coefficient is ∼10⁵ cm⁻¹ and the band gap is between 0.86 eV and 0.95 eV. The band gap showed dependence on CTS phase. The morphology of the samples is like petals. The sample that has the best characteristics to be applied as absorber film on photovoltaic devices is the sample C10T1-245 (0.1 M (SnCl₂ · 2H₂O), 0.1 M (CuCl₂ · 2H₂O), 0.3 M (CS(NH₂)₂) with temperature annealing of 245 °C. (paper)