Optical and optoelectrical characterizations of Cu 2 ZnSn 3 S 8 : A potential nominee for optoelectronic and photovoltaic applications M.S. Alkhalifah a , I.M. El Radaf a,b , M.S. El-Bana a,c,* a Department of Physics, College of Science, Qassim University, Qassim, Buraydah 51452, Saudi Arabia b Electron Microscope and Thin Films Department, Physics Research Institute, National Research Centre, Dokki, Giza 12622, Egypt c Nanoscience & Semiconductor Laboratories, Department of Physics, Faculty of Education, Ain Shams University, Cairo, Egypt A R T I C L E INFO Keywords: Stable phase of Cu 2 ZnSn 3 S 8 Energy gap Optical properties Window layer in thin flm solar cell Zinc Compounds ABSTRACT A successful trial has been accomplished in synthesizing a stable phase of Cu 2 ZnSn 3 S 8 (CZTS 8 ). The deposited thin flms have been obtained by utilizing the chemical bath deposition (CBD) process. Basic characterizations have been applied to check the formation of our new stable material. The formed CZTS 8 flms disclose the amorphous nature as presented in the x-ray diffraction (XRD) patterns. Also, an enhancement in flm morphology has been obtained by expanding the flm thickness. Moreover, optoelectrical and linear/nonlinear optical fea- tures have been studied for the as-deposited flms. Our material has interesting characteristics to be a promising window sheet for thin flm solar cells. It reveals a tendency to be an n-type semiconductor material. Further, it shows high optical absorption as well as high optical conductivity. Moreover, it has a direct optical transition, and its energy gap is varied in the range (3.89 eV - 3.94 eV). Additionally, the dispersion and optoelectrical indices were affected by the variation in both flm thickness and flm roughness. Furthermore, the nonlinear optical indices χ (1) , χ (3) and n 2 were improved via the increase in flm thickness. A satisfactory correlation has been performed between all of the evaluated parameters. The main goal of this study has been achieved by obtaining n-type material by increasing the Tin and Sulfur contents in the CZTS 8 as compared with the known p- type material (Cu 2 ZnSnS 4 ) CZTS 4 . The revealed fndings acknowledge that CZTS 8 could be a promising nominee for either optoelectronic or photovoltaic applications. 1. Introduction Many researchers’ efforts have recently been directed toward photovoltaic and renewable energy. Their efforts have been focused on synthesizing novel materials that are both economical and effective light harvesting materials. Such materials could be used as either new ab- sorbers or window sheets in thin-flm solar cells (TFSC). Examples of these materials are CdS, CuInGa(S, Se) 2 (CIGS), and CdTe. Some of them act as adequate window sheets in the TFSC as a result of their wide bandgap such as CdS thin flm [1–6]. At the same time, others are known as excellent absorber layers in solar cells by virtue of their narrow bandgap such as CIGS [7–9]. However, the high cost of elements such as (In, Ga) directed the researchers to search for earth-abundant and eco- nomic semiconducting materials such as the quaternary I-II-IV-VI system (I= Cu or Ag, II= Zn, Cd, In, IV= Ge or Sn, and VI = Se or S). This system can be split into two groups (I 2 -II-IV-VI 4 ) and (I 2 -II-IV 3 -VI 8 ) based on the concentration of the IV & VI elements [10,11]. The materials of this system attracted more interest owing to their remarkable electrical and optical properties, as well as their chemical stability, economic cost, and earth-abundancy. The I 2 -II-IV-VI 4 (I = Cu, VI = S) compounds are reported to act as light-absorbing materials. They have narrow bandgap energy (E g ≈ 1.5 eV), and a suitable absorption coeffcient [12,13]. They are promising p-type semiconductors. Hence, they act effectively as absorber sheets in thin-flm solar cells. For example, Son et al. reported that Cu 2 ZnSn(S, Se) 4 revealed direct optical transition with an energy gap that varies in the range of 1 eV – 1.5 eV. Also, their materials showed the p-type conductivity [14]. Kumar et al. reported also that Cu 2 CdSnS 4 behaves as a p-type layer in thin flm solar cells and it has an energy gap of 1.65 eV [15]. Liu et al. displayed that Cu 2 XSnR 4 (X=Zn, Cd; R=S, Se) materials have an energy gap in the range of 0.95 eV – 1.49 eV and all of them are p-type semiconductors [16]. Also, Ram- asamy et al. showed that CuGaSnS 4 has a direct energy gap of 1.17 eV and CuInSnS 4 has a direct energy gap in the range of 1.3 eV – 1.4 eV * Corresponding author at: Department of Physics, College of Science, Qassim University, Qassim, Buraydah 51452, Saudi Arabia. E-mail addresses: m.elbana@qu.edu.sa, mohammed.el-bana@bath.edu (M.S. El-Bana). Contents lists available at ScienceDirect Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jalcom https://doi.org/10.1016/j.jallcom.2024.176768 Received 6 July 2024; Received in revised form 18 September 2024; Accepted 27 September 2024 Journal of Alloys and Compounds 1008 (2024) 176768 Available online 30 September 2024 0925-8388/© 2024 Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.