Synthesis of colloidal CuInSe₂ nanoparticles by electrical spark discharge in liquid

Abstract

This work presents a low-cost, non-vacuum, and facile process for fabrication of CuInSe₂ (CIS) nanoparticles using electrical discharge treatment of mixture of copper, indium, and selenium powders between two tungsten electrodes immersed in pure ethanol. The synthesized particles were characterized by UV-Vis-NIR absorption, X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), Raman spectroscopy, transmission and scanning electron microscopy (TEM and SEM). TEM images exhibited that the final product is mainly composed of a large amount of primary nanoparticles typically 10–40 nm in diameter. The band gap energy value of the nanoparticles was estimated to be around 1.2 eV. The XRD pattern of the as-prepared samples besides the main peaks of chalcopyrite tetragonal CIS showed the diffraction peaks which could be attributed to intermediate phases. To omit the intermediate phases and reach to pure CIS nanoparticles the as-prepared in electrical discharge samples were annealed in vacuum at the temperature of 700 °C during 90 min. The XRD and SEM analysis results of annealed samples clearly indicated that chalcopyrite CuInSe₂ particles with good crystallinity and near stoichiometric atomic composition were obtained. The composition and crystalline structure of the product was also confirmed by the room-temperature Raman spectrum showing an intense peak at 172 cm^-1 corresponding to the A₁ phonon mode of tetragonal CuInSe₂ chalcopyrite.