Investigation of Optoelectronic Properties of HfClBr Janus Monolayer under the Biaxial Strain Effect

Abstract

In general, the transition elements, including Hafnium (Hf), have become the focus of researchers' attention, as when they combine with chalcogens and halides, they turn into semiconductors with distinct energy gaps. Moreover, chalcogens and halides are desirable in scientific research when forming layers or membranes. The Janus monolayer is unique two-faced material composed of two different chemical species on opposite sides of a single layer. Herein, we use first-principles simulations to thoroughly investigate the electrical and optical properties of this material. Our calculations reveal that the Bromochlorohafnium (HfClBr) Janus monolayer is an indirect semiconductor at equilibrium, with an energy gap of 0.928 eV and changing from 0.532 eV to 1.233 eV after applying the biaxial strain, as determined by the Perdew-Burke-Ernzerhof (PBE) method. The results indicate that the Janus HfClBr monolayer has a competitive advantage over other materials for use in solar cells and energy storage devices due to its unique optical and electrical characteristics. Furthermore, our analysis showed that the optical and electrical characteristics of the Janus HfClBr monolayer are significantly impacted by biaxial strain, with the ability to absorb light in both the visible and ultraviolet spectral regions. Additionally, the first optical gap of the Janus HfClBr monolayer is found to be shiftable under the biaxial strain, suggesting potential applications in nano-electronics, particularly in the field of solar cells.

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“…The complex dielectric function is a frequency-dependent parameter used in analysing the optical response, and it is composed of two parts related to each other by the eqn (3). 28,29,36–38 ε ( ω ) = ε 1 ( ω ) + jε 2 ( ω )where ε 1 ( ω ) = n 2 ( ω ) − k 2 ( ω ) is the real part, while ε 2 ( ω ) = 2 nk is the imaginary part of the dielectric function, with n and k being the refractive index and extinction coefficient, respectively. ε 1 ( ω ) represents the dispersion of the incident photon by the material, and ε 2 ( ω ) represents the energy absorption by the material and relates to the optical transition from the valence band to the conduction band of a semiconductor material.…”