Cubic Germanium monochalcogenides (π-GeS and π-GeSe): Emerging materials for optoelectronic and energy harvesting devices. (June 2019)

• Record Type: Journal Article
• Authors: Ur Rehman, Sajid; Butt, Faheem K.; Tariq, Zeeshan; Ul Haq, Bakhtiar; Lin, Guochen; Li, Chuanbo
• Is Part Of: Solar energy. Volume 185(2019)
• Page Start: 211
• Page End: 221
• Publication Date: 2019-06
• Subjects: Cubic chalcogenides -- Germanium -- DFT -- Optical properties -- Mechanical properties -- Anisotropy elasticity; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2019.03.090
• Languages: English
• ISSNs: 0038-092X

Abstract

Graphical abstract: Highlights: First ever optical, mechanical and anisotropic properties of cubic GeX (X = S, Se) are studied. 2D & 3D surface visualization suggest that both chalcogenides are elastically anisotropic. Debye temperature (θD ) of π-GeS and π-GeSe are 262.28 K and 264.46 K, respectively. Germanium chalcogenides are promising candidate for optoelectronic, thermoelectric devices. Abstract: Newly discovered cubic phase of Germanium monochalcogenide (π-GeS and π-GeSe) with a moderate bandgap, less toxicity, and novel electronic properties have earned significant attention of researchers due to appropriate nature for the energy-related applications such as photovoltaic, optoelectronic and thermoelectric devices. The structural, electronic (band structure and DOS), optical and elastic properties of π-GeS and π-GeSe have been studied by ultrasoft pseudopotential technique. The band structure calculations confirm that both π-GeS and π-GeSe are indirect in nature with bandgap energies 1.38 and 1.04 eV respectively. The first-time calculated elastic constants of π-GeS and π-GeSe satisfy their mechanical stability criteria (Born stability). The elastic moduli (bulk, Young's, shear), Lame's parameters, Poisson's ratio, Debye temperature, and average sound velocity are determined by Voigt-Reuss-Hill approximation. The shear and Young's elastic properties reveal that both π-GeS and π-GeSe are anisotropic, which is also confirmed from 2D and 3D surface visualization. The calculated Debye temperature (θD ) of π-GeS and π-GeSe are 262.28 K and 264.46 K at 300 K, respectively. Additionally, the longitudinal and transversal waves sound velocities are calculated for the first time in [1 1 1], [1 1 0] and [1 0 0] directions. The present results reveal that π-GeS and π-GeSe could be appropriate candidates for exploitation in energy storage, optoelectronic and thermoelectric devices. Particularly GeS, which has higher absorption peaks and optimum bandgap (1.38 eV) for practical photovoltaic and photo-sensing applications. The present work provides the pathways for theoretical and experimental studies on electronic devices based upon cubic chalcogenides.