Study of the Stoichiometry Effect on the Structure and Loss Kinetics of Photogenerated Current Carriers in Cu2-δBaSnS4 (0≤δ≤0.4) Quaternary Copper Compounds

The solid-phase method was applied to synthesize Cu2-delta BaSnS4 (0 <=delta <= 0.4) polycrystalline powders. The lattice parameters were refined. It was shown that the crystal structure parameters changed. For the first time, Raman spectra were experimentally obtained for copper-deficient samples. It was found that some difference in the position of major peaks is due to the Cu2-delta BaSnS4 structure changing with increasing delta, as well as a partial valence change in tin or copper atoms. Using X-ray photoelectron spectroscopy, it was shown that when going from Cu2BaSnS4 to Cu1.6BaSnS4, there was no change in the valence state of copper, but the valence state of tin particularly changed. The lifetimes of the current carriers in the synthesized samples were significantly less than 10 ns.