Simulation of Raman Spectra for Cu2ZnSn(SxSe1-x)4 Using DFT Calculations
Cu2ZnSnS4 (CZTS) is an important material for solar cell applications. It has an ideal bandgap of ~1.45 eV for absorbing the solar radiation and has a high absorption coefficient >104 cm-1. All the elements making CZTS are abundantly available within the earth’s crust, inexpensive, and environmentally benign. CZTS exists in a tetragonal lattice in which the metal cations occupy the tetrahedral voids within the sulfur anion lattice. Depending on the arrangement of the cations within the tetrahedral voids of the anion lattice, there exist three different phases of CZTS that cannot be distinguished using x-ray diffraction (XRD) as all of them have similar crystal structures. For the same reason, it is also not possible to use XRD for distinguishing CZTS from the impurity phases of Cu2SnS3 (CTS) and ZnS. However, it has been shown that Raman spectroscopy can be used to differentiate CZTS, CTS and ZnS. In an earlier work, these researchers have simulated the Raman spectra for CZTS using DFT and suggested that Raman spectroscopy, in conjunction with ab initio calculations, can be used as an experimental technique to differentiate the three phases of CZTS. They are now simulating the electronic and structural properties of a series of CZTS-CZTSe alloys and studying the effect of anion ordering on the alloy properties.