Morphological and Compositional Analysis of Electrodeposited Indium (III) Sulfide (In₂S₃) Films

Abstract

Within the last few years, there has been notable progress in understanding the growth mechanisms of semiconductor thin films for photovoltaic (PV) applications. Electrodeposition continues to be a complex deposition technique that can lead to regions of low quality (for example, cracks) in films. Such cracks can form porous zones on the substrate and diminish the heterojunction interface quality of a PV cell. In this paper, electrodeposition of In 2 S 3 films was systematically and quantitatively investigated by varying electrodeposition parameters including bath composition, current density, deposition time, and deposition temperature. Their effects upon the morphology, composition, and film growth mechanism were studied with the help of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and digital imaging analysis (using fracture and buckling analysis software). In addition, the effect of different annealing treatments (200 • C, 300 • C, and 400 • C in air) and coated glass-substrates (Mo, ITO, and FTO) upon the properties of the In 2 S 3 films was analyzed. Furthermore, the Taguchi/Design of Experiments (DOE) Method was used to determine the optimal electrodeposition parameters in order to improve the properties. Indium (III) sulfide (In 2 S 3 ) is a promising semiconductor material (III-VI compound), suited for many technological applications like optoelectronic, 1 photovoltaic, 2 and photoelectric devices 3 due to its stability, large energy bandgap (∼2.3 eV), and photoconductive behavior. 4 β-In 2 S 3 is an n-type semiconductor material that has been considered as a non-toxic substitute for cadmium-containing PV cells. 5 It has potential to replace cadmium sulfide (CdS) as a buffer layer in copper indium gallium selenide/sulfide (CIGS)-based PV cells due to environmental concerns. 6 Several reports have been published on synthesis of In 2 S 3 films by numerous deposition techniques. These films have exhibited diverse morphologies and structural properties. 7-11 In In 2 S 3 (from atomic layer deposition)-based CIGS PV cells, an efficiency of 16.4% 12 has been achieved, which is few percent less than the 20.8% efficiency reported for CdS-based CIGS PV cells with the CdS deposited by chemical bath deposition (CBD). 13 Electrodeposition is considered an economical and time-saving alternative to vacuum-based techniques for depositing semiconductor thin films onto a substrate with full coverage and high growth yield. 14 It offers high material utilization efficiency, precise control with proper bath chemistry, and in-situ monitoring. 14,15 In 2011, electrodeposited In 2 S 3 -based CIGSe PV cells yielded an energy conversion efficiency of 10.2%. 16 However, electrodeposition still remains a complex technique for synthesizing thin films due to several deposition parameters, which can affect the properties of the films. 17,18 Poor adhesion, nonuniformity, flaking, and cracking 19 of films are common problems when electrodepositing films onto smooth surfaces, 14 as nucleation and growth...

Progress in indium (III) sulfide (In 2 S 3 ) buffer layer deposition techniques for CIS, CIGS, and CdTe-based thin film solar cells

“…Our work at the Optoelectronic Materials Research Laboratory (OMRL)-ASU focuses upon electrodeposition of CuInS 2 and In 2 S 3 (Mughal et al, , 2015 films using organic electrolytes, and the ultimate goal is to fabricate n-In 2 S 3 /p-CuInS 2 heterojunction TFSC. In this paper, we highlight the progress and development of In 2 S 3 -buffered TFSCs by various deposition techniques.…”

“…Indium (III) sulfide (In 2 S 3 ), an indium chalcogenide, is a III-VI semiconductor compound important for optoelectronic (Cansizoglu et al, 2010;Mughal et al, 2015), photoelectric (Ho, 2011), and photovoltaic (PV) applications Haleem et al, 2012 due to its stable chemical composition (Newell et al, 2011;Strausser et al, 1995), photoconductivity (Gilles et al, 1962), and luminescent characteristics (Springford, 1963) at ambient conditions. It functions as an n-type semiconductor with an optical bandgap of 2.1-2.3 eV Dutta et al, 2007); however, there is still controversy about whether it is has a direct or indirect bandgap.…”

“…In 2 S 3 crystallizes into three allotropic forms, namely, a-In 2 S 3 (cubic structure between 420°C and 754°C), b-In 2 S 3 (tetragonal structure below 420°C), and c-In 2 S 3 (trigonal structure above 754°C) (Lee et al, 2008). Among these crystallographic phases, b-In 2 S 3 has the widest applications (Mughal et al, 2015) due to its defective spinal structure (most stable) Tao et al, 2008, large photosensitivity (Warrier et al, 2013), and physical characteristics (Cansizoglu et al, 2010). With optimal physical properties, it can meet the requirement of a suitable buffer layer in TFSCs.…”