Contents lists available at ScienceDirect Ceramics International journal homepage: www.elsevier.com/locate/ceramint Deposition of Cu 2 ZnSnS 4 films by doctor blade printing using a one-step microwave heated ink as an absorber layer for solar cells Mahnaz Karbassi a , Saeid Baghshahi b,* , Nastaran Riahi- Noori c , Roozbeh Siavash Moakhar c a Department of Materials Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran b Department of Materials Science and Engineering., Faculty of Engineering, Imam Khomeini International University, Qazvin, Iran c Non-Metalic Materials Research Group, Niroo Research Institute (NRI), Tehran, Iran ARTICLE INFO Keywords: CZTS film Solar cell Microwave heating process UV–Vis spectrophotometry ABSTRACT Kesterite (Cu 2 ZnSnS 4 , CZTS) semiconductors are known as the most suitable compounds for the synthesis of absorber layers. These compounds are used in solar cells due to their high solar energy absorption coefficient and ideal band gap. In the present work, the microwave-assisted process and doctor blade printing were used to prepare Cu 2 ZnSnS 4 films. To this aim, ink solution was used, which consisted of copper, zinc acetate, tin chloride and thiourea as copper, zinc, tin and sulfur precursors, respectively. Ethylene glycol was used as a non-toxic solvent. The CZTS ink was prepared using microwave heating for 10 min. The CZTS layers were printed on soda lime silica glass substrates and heat treated at 150, 200, 250, 300, and 350°C. The microstructure, phase ana- lysis, morphology, optical properties, and absorption ratio of the samples were evaluated using X-ray diffraction analysis, Raman spectroscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis, trans- mittance spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive X-ray, and UV–Vis spectrophotometry. The formation of the Kesterite structure was confirmed using X-ray diffraction and Raman spectroscopy. The FESEM micrographs and DLS (dynamic light scattering) revealed that the films con- tained equated grains with the diameter range of 350–650 nm. According to the X-ray analysis and Raman spectrum, the highest crystallization and purity of the Kesterite phase as well as the best microstructure property and morphology (smooth spherical particles with good adhesion) of the CZTS films were found in the synthe- sized specimen at 300°C. The band gap of the samples was measured to be about 1.5 eV using UV–Vis spec- trophotometry. 1. Introduction Producing carbon-free, readily accessible, clean, efficient and cheap green energy with consideration of vital factors is a great global con- cern. Various solar cells are widely demanded for clean energy pro- duction [1–3]. Common solar cells are prepared using silicon (Si), cadmium telluride or copper indium gallium selenide (CIGS), which are not yet cost effective. For this reason, a comprehensive research has been carried out to identify and make possible the use of new materials that can develop affordable power [4–9]. The copper zinc tin sulphide (Cu 2 ZnSnS 4 ) quaternary compound semiconductor with a Kesterite structure is known as a proper potential material for solar cell pro- duction with low cost and high efficiency. CZTS has a low direct band gap (p-type) of 1.5 eV and high absorption coefficient of 10 4 cm -1 [10–13]. Microwave processing is a suitable method for synthesis of various materials such as metals, oxides, sulphides and halides due to its high speed [14]. Microwave heating is a metaphysics process, which is a combination of electromagnetic waves and heat transfer [15]. In mi- crowave processing, the right choice of solvent is highly important. The solvent must be able to both absorb the microwave energy and trans- form it to heat. Based on the Shockley-Queisser estimate in the theo- retical calculation, CZTS has about 32.2% efficiency, While, the highest efficiency of CZTS solar cells prepared by hydrazine solution was re- ported to be 9.66%. However, hydrazine is harmful, flammable and unstable [16]. Other solvents such as water [17] and oleylamine [18] have also been used for this purpose, but no significant progress has been made so far. Hence, it is critical to find a suitable alternative so- lution for preparation of nanoparticles with high quality. Based on the results of some studies that used ethylene glycol [19–21] for absorbing ink, an ethylene glycol solution was used in the present study to prepare ink. https://doi.org/10.1016/j.ceramint.2019.09.223 Received 16 July 2019; Received in revised form 10 September 2019; Accepted 23 September 2019 * Corresponding author. E-mail address: baghshahi@eng.ikiu.ac.ir (S. Baghshahi). Ceramics International xxx (xxxx) xxx–xxx 0272-8842/ © 2019 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Please cite this article as: Mahnaz Karbassi, et al., Ceramics International, https://doi.org/10.1016/j.ceramint.2019.09.223