Microwave assisted synthesis, characterization and thermoelectric properties of nanocrystalline copper antimony selenide thin films

Abstract

In the present work, we have synthesized p-type copper antimony selenide (Cu₃SbSe₄) thin films in an aqueous alkaline medium using a microwave assisted synthesis technique. The deposited thin films were characterized by UV-Vis-NIR spectroscopy, X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM) and thermoelectric techniques. On the basis of experimental results, a possible reaction mechanism has been discussed in detail. The band gap of the as deposited film is 1.94 eV and after annealing it reaches 1.87 eV for Cu₃SbSe₄. XRD results indicate that the as deposited thin films of CuSbSe₂ have an orthorhombic crystal structure with secondary mixed phases and after annealing this is converted to Cu₃SbSe₄ having a pure tetragonal crystal structure. FESEM micrographs of Cu₃SbSe₄ showed a spherically diffused granular morphology having an average grain size of 25 nm. The HRTEM result of Cu₃SbSe₄ shows good crystallinity with a lattice spacing of 0.327 nm along the (112) plane. The EDS spectrum shows the presence of Cu, Sb and Se elements. The thermoelectric figure of merit (ZT) of the as deposited film is calculated to be 0.059 at 300 K and that of annealed Cu₃SbSe₄ is found to be 0.141 at 300 K.