Facile synthesis and size-dependent optical properties of luminescent ZnIn2S4 nanocrystals derived from metal xanthates

Abstract

ZnIn₂S₄ (ZIS), a ternary semiconductor with photo-absorption in the visible region of the solar spectrum, is a promising active material for catalysis, optoelectronics and photoconductors and exists in various morphologies. Synthesis of phase-pure ZIS nanocrystals (NCs) devoid of any binary or biphasic impurities is highly necessary for device applications. The present investigation deals with facile synthesis of hexagonal phase ZIS spherical NCs by thermolysis of tris isopropylxanthate of indium and bis isopropylxanthate of zinc in oleylamine (OAm) at 280 °C for different durations (10, 15 and 20 min). The crystal structure, phase purity, elemental composition, morphology and band gap of the as-synthesized ZIS NCs were thoroughly evaluated by powder X-ray diffraction (pXRD), Raman, energy dispersive X-ray spectroscopy (EDS), electron microscopy tools and diffuse reflectance spectroscopy (DRS), respectively. The size-dependent optical band gap and emission maximum were tuned in the range of 3.18 to 2.40 eV and 440 to 528 nm by adjusting the reaction time from 10 to 20 minutes. Size-dependent quantum yields (QYs) in the range of 7–11% have been achieved for these NCs. Lifetime measurements performed on these samples show lifetimes in the range of 1.3–1.5 ns for the fast-decaying component and 5.7–7.3 ns for the slow decaying component.