On the structural, electronic, optical and thermoelectric properties of CdIn2Se4 ordered-vacancy compound
Graphical abstract
Introduction
So far, AB2C4-type ordered-vacancy compounds (OVCs) have been extensively investigated and considered as a bridge between crystal and impurity physics [[1], [2], [3], [4]]. Due to the peculiar crystal structure, this kind of compounds possesses intriguing physical properties such as high photosensitivity and nonlinear-optical properties [5,6]. In addition, these materials have been proven to be suitable for photovoltaic applications [6,7].
In particular, the CdIn2Se4 OVC compound has been investigated experimentally with results showing evidence that depending on the synthesis conditions, its tetragonal structure can be deformed with lattice constant ratio c/a being 1, 2 and 3, which is termed as α, β and γ phase, respectively. In these phases, some aspects of the crystal structure of β and γ phases have not been totally clarified [8]. In the case of α phase, the crystal structure effect on its valence band was early investigated by Picco et al. [9] using UV photoemission spectroscopy. Later, the structural and electronic properties were theoretical studied by James et al. [10] and Mariano et al. [11]. Experimentally, Nikale et al. [12] demonstrated the these kinds of compounds to possess a good photovoltaic activity. Despite α-CdIn2Se4 has been a subject of some scientific investigations, its electronic and optical properties have not been investigated well. Therefore, we consider necessary to perform a systematic study on these properties, where the results can be useful for designing its optoelectronic applications. Additionally, its thermoelectric applicability has not been explored yet.
The main aim of this work is to investigate the structural, electronic, optical and thermoelectric properties of CdIn2Se4 compound. For such aim, a series of first-principles calculations based on the density functional theory and semiclassical transport Boltzmann theory has been performed. Based on our calculations, CdIn2Se4 is a direct semiconductor with band gap of 1.834 eV predicted by mBJ potentials. Results suggest that it is a promising absorber in the ultraviolet region with high absorption coefficient. Additionally, with high figure of merit values, this material can be used in thermoelectric applications. However, a p-type title should be more favorable than a n-type title. Our findings can be a good reference for future works treating the CdIn2Se4 compound as well as other AB2C4 family.
Section snippets
Computational details
Theoretical calculations based on the density functional theory (DFT) [13] have been carried out to study the structural, electronic, optical and thermoelectric properties of CdIn2Se4 compound. The Wu-Cohen scheme within the generalized gradient approximation (GGA-WC) [14] and Tran-Blaha modified Beck-Johnson semilocal exchange (mBJ) potential [[15], [16], [17]] are adopted to determine the electron exchange-potential potentials. The basis set within the full-potential linearized augmented
Structural properties
Under ambient conditions, the CdIn2Se4 compound can crystallize in a tetragonal structure with lattice parameters ratio c/a = 1 (which also called pseudocubic), space group P2m (no. 111). Experimentally reported, the Wyckoff atomic positions of Cd, In and Se atoms are (0; 0; 0), (0.5; 0; 0.5) and (0.7246; 0.7246; 0.2306), respectively, and the lattice constant is a = c = 5.818 (Å) [5]. The crystal structure of this ternary is illustrated in Fig. 1a. It can be described through the zinc
Conclusions
In summary, the structural, electronic, optical and thermoelectric properties of the CdIn2Se4 compound have been determined using FP-LAPW calculations and analyzed in detail. The calculated structural parameters agree well with other results available in the literature. As predicted by the reliable mBJ potential, the CdIn2Se4 compound is a direct semiconductor with ab electronic band gap of 1.834 eV. DOS profile indicates that Se-p is the main responsible of the valence band, while the In-s,
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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