Fig. 1 Schematic diagram of thermal cycle followed in melt-quench method (T max = 1323 K)

Fig. 2 XRD patterns of CuIn(SexTe1-x)2 system in the 2θ range 24.5-27.0: a x = 0.1, b x = 0.2, c x = 0.4, d x = 0.5, e x = 0.6, f x = 0.8, g x = 0.9

Fig. 3 a XRD pattern and the results of Rietveld refinement for CuIn(Se0.1Te0.9), the crosses and the overlying solid line represent the experimental data and the calculated profile, respectively, and the short vertical markers indicate possible Bragg reflections, whereas the bottom curve denotes the difference between the experimental and calculated data, b inset shows the enlarged view of 112 reflection, c inset shows the spectrum in the 2θ range of 80°-130°, on an expanded scale

Fig. 4 a XRD pattern and the results of Rietveld refinement for CuIn(Se0.5Te0.5)2, the crosses and the overlying solid line represent the experimental data and the calculated profile, respectively, and the short vertical markers indicate possible Bragg reflections, whereas the bottom curve denotes the difference between the experimental and calculated data, b inset shows the enlarged view of 112 reflection, c inset shows the spectrum in the 2θ range of 80°-130°, on an expanded scale

Fig. 5 Schematic of phase formation in CuIn(SexTe1-x)2. Dark vertical lines are just markers. Grey vertical lines represent percentage (lengthwise) of the phases

Fig. 6 Variation of lattice parameters with selenium content (X). Open circles denote ‘a’ whereas solid circles represent ‘c’

Fig. 7 CuInSe2-CuInTe2 (CuIn(SexTe1-x)2) phase diagram reproduced from Bodnar et al. [32]

Fig. 8 Raman spectra of a CuIn(Se0.1Te0.9)2 and b CuIn(Se0.5Te0.5)2, the symbols, lines and dark line show the experimental data, individual Lorentzians and the overall fit, respectively

Fig. 9 Basic tetrahedral in a CuInTe2-like, b CuInSe2-like and c with statistical distribution of Te and Se atoms in CuIn(SexTe1-x)2

Fig. 10 Results of A 1 mode analysis for CuIn(SexTe1-x)2, the average force constants for the calculations are taken from the results of the Rietveld refinement