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<p>Twist-angle engineering in two-dimensional (2D) van der Waals (vdW) heterostructures has emerged as a powerful strategy for tailoring electronic, optical, and transport properties of bilayer transition metal dichalcogenides (TMDs). In this study, we present a comprehensive first-principles investigation of AB-stacked bilayer molybdenum diselenide (2L-MoSe<sub>2</sub>), where one monolayer is twisted relative to the other by a range of commensurate angles (0°, 21.79°, 38.21°, and 60°). Notably, at a twist angle of 38.21°, the system undergoes a transition from an indirect- to a direct-bandgap semiconductor with a bandgap of 1.43&#xa0;eV, closely resembling monolayer MoSe<sub>2</sub>. This transition is attributed to the enhanced contribution of the K-point in the valence band, making the 38.21° configuration particularly promising for optoelectronic applications. Furthermore, our calculations reveal that interlayer spacing increases with twist angle, enhancing sensitivity to out-of-plane perturbations. The electron localization function (ELF) analysis confirms the absence of interlayer charge localization, indicating weak interlayer hybridization across all twist configurations. Optical absorption spectra exhibit a redshift and reduced intensity at 21.79° and 38.21°, suggesting improved crystalline quality and suppressed excitonic recombination. The 38.21° configuration demonstrates strong absorption in the red-light region (700–780&#xa0;nm), favorable for photovoltaic applications, and nearly zero absorption in the UV-A range (315–400&#xa0;nm), ideal for ultraviolet filtering. These findings highlight the potential of 2L-MoSe<sub>2</sub> with a 38.21° twist as a tunable, direct-bandgap material for next-generation electronic, optoelectronic, and photovoltaic devices.</p>

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Impact of Twist Angle on the Electronic, Optical, and Transport Properties of Bilayer MoSe2: A DFT Study

  • 期刊论文

  • 发表日期：

    2025年8月9日

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  • Alok Singh,
  • Savita Singh

摘要

Twist-angle engineering in two-dimensional (2D) van der Waals (vdW) heterostructures has emerged as a powerful strategy for tailoring electronic, optical, and transport properties of bilayer transition metal dichalcogenides (TMDs). In this study, we present a comprehensive first-principles investigation of AB-stacked bilayer molybdenum diselenide (2L-MoSe2), where one monolayer is twisted relative to the other by a range of commensurate angles (0°, 21.79°, 38.21°, and 60°). Notably, at a twist angle of 38.21°, the system undergoes a transition from an indirect- to a direct-bandgap semiconductor with a bandgap of 1.43 eV, closely resembling monolayer MoSe2. This transition is attributed to the enhanced contribution of the K-point in the valence band, making the 38.21° configuration particularly promising for optoelectronic applications. Furthermore, our calculations reveal that interlayer spacing increases with twist angle, enhancing sensitivity to out-of-plane perturbations. The electron localization function (ELF) analysis confirms the absence of interlayer charge localization, indicating weak interlayer hybridization across all twist configurations. Optical absorption spectra exhibit a redshift and reduced intensity at 21.79° and 38.21°, suggesting improved crystalline quality and suppressed excitonic recombination. The 38.21° configuration demonstrates strong absorption in the red-light region (700–780 nm), favorable for photovoltaic applications, and nearly zero absorption in the UV-A range (315–400 nm), ideal for ultraviolet filtering. These findings highlight the potential of 2L-MoSe2 with a 38.21° twist as a tunable, direct-bandgap material for next-generation electronic, optoelectronic, and photovoltaic devices.