Contents lists available at ScienceDirect Ceramics International journal homepage: www.elsevier.com/locate/ceramint Fabricating chalcogenide Cu 2 ZnSnS 4 (CZTS) nanoparticles via solvothermal synthesis: Effect of the sulfur source on the properties E.M. Mkawi a,b,* , Y. Al-Hadeethi a , E. Shalaan a , E. Bekyarova c a Department of Physics, Faculty of Science, King Abdulaziz University, 21589, Jeddah, Saudi Arabia b Center of Nanotechnology, King Abdulaziz University, 42806, Jeddah, Saudi Arabia c Department of Chemistry, University of California at Riverside, Riverside, CA, 92521, USA ARTICLE INFO Keywords: Cu2ZnSnS4 (CZTS) nanoparticles Solvothermal method XRD ABSTRACT In the present investigation, we successfully synthesized Cu 2 ZnSnS 4 (CZTS) nanoparticles via solvothermal method with different sulfur sources at 240 °C for 14 h. The experimental results show that the different sulfur sources caused unique and significant changes in the material properties. The synthesized products were in- vestigated by XRD. Raman spectroscopy revealed that the crystallinity improved and kesterite structures with no secondary phases formed. The TEM results showed that the morphological features of the prepared CZTS na- noparticles had an average particle size of 40 nm and confirmed the nanoparticles' crystallinity. The FESEM results demonstrated that the CZTS nanoparticles had thin films with dense, uniform, and smooth surfaces with grain sizes in a range of 2–4 μm. The CZTS nanoparticles’ optical band gaps were 1.51 eV. XPS was used to investigate the oxidation state of elements in a sample prepared using thiourea. Photovoltaic devices with SLG/ Mo/CZTS/CdS/i-ZnO/ZnO:Al structures exhibited3.56% efficiency via CZTS thin film-based nanoparticles pre- pared using thiourea. 1. Introduction At present, total global power consumption is approximately 16 TW. Forecast temperatures will reach 45 TW by 2100, with a forecast temperature increase of 6 °C. Researchers have developed many types of materials to obtain low-cost, non-toxic, and highly efficient thin film solar cells. Chalcogenide compounds used in solar cell fabrication in- clude tellurides (CdTe),sulfides(CIS), and selenides (CIGSe) [20]. Many types of materials are used in solar cell applications. Kesterite structures are superior because they have direct energy gaps suitable for the solar spectrum with a high electron affinity and high thermal sta- bility. The most important properties of chalcogenide materials are low absorber layer thicknesses. These materials are inexpensive and have excellent light-absorbing properties and a low environmental impact [22]. Quaternary Cu 2 ZnSnS 4 (CZTS) thin film is a semiconductor ma- terial used as a p-type for solar cell applications. It has low toxicity, suitable optical energy gap in a range of ~1.5-1.9 eV, a high absorption coefficient (α > 10 4 cm -1 ), and is an environmentally friendly abundant element and a potentially low-cost precursor [13,14]. Kes- terite CZTS has been developed using many techniques, such as electron beam deposition, evaporation, electrochemical deposition, sputtering, and nanostructure-based film casting [10,11,19,25,27]. Thin films produced via nanostructure-based solutions have many advantages such as a low cost, large scale, and easy control. Many methods are used to deposit nanoparticles ink on conductive glass substrates, such as spin-coating, dip-coating, and continuous roll- to-roll processing. Hydrothermal synthesis is a useful method of fabri- cating high-quality materials under various conditions. For CZTS, the hydrothermal method produces pure phase, good crystallinity CZTS nanostructures without sulfurization [12]. The roles of surfactants, solvents, and complex agents are very important, as they impact the morphological properties and crystalline nature of CZTS nanostructures Hydrazine-based and molecular ink-based solution processes produce 10% efficiencies. These processing methods deposit CZTS nanoparticles onto conductive back contacts followed by sulfurization at tempera- tures higher than 500 °C. Sulfurization produces variable grain sizes of film and high-quality CTZS crystalline phases, reduces defects and grain boundary concentrations, and improves the charge transport char- acteristics of films. This step can lead to variations in the composition (the Zn/Sn and Cu/(Zn + Sn) ratio) and impurity of secondary phases, which effects sulfur incorporation in solar cell devices. Non-stoichiometry CZTS synthesis produces anti-site defects (CuZn), secondary phases, such as Cu 2 S, and SnS 2 , and CTS, interstitials (Cu i ), vacancies (V Cu ), and defect clusters (Cu + ZnCu). Some zinc https://doi.org/10.1016/j.ceramint.2020.06.276 Received 6 June 2020; Received in revised form 24 June 2020; Accepted 25 June 2020 * Corresponding author. Department of Physics, Faculty of Science, King Abdulaziz University, 21589, Jeddah, Saudi Arabia. E-mail address: moizmerghni@yahoo.com.my (E.M. Mkawi). Ceramics International xxx (xxxx) xxx–xxx 0272-8842/ © 2020 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Please cite this article as: E.M. Mkawi, et al., Ceramics International, https://doi.org/10.1016/j.ceramint.2020.06.276