Strain-Induced Tunable Band Offsets in Blue Phosphorus and WSe2 van der Waals Heterostructure

Temperature-Dependent Phonon Scattering and Photoluminescence in Vertical MoS2/WSe2 Heterostructures

Transition metal dichalcogenide (TMD) monolayers and their heterostructures have attracted considerable attention due to their distinct properties. In this work, we performed a systematic investigation of MoS2/WSe2 heterostructures, focusing on their temperature-dependent Raman and photoluminescence (PL) characteristics in the range of 79 to 473 K. Our Raman analysis revealed that both the longitudinal and transverse modes of the heterostructure exhibit linear shifts towards low frequencies with increasing temperatures. The peak position and intensity of PL spectra also showed pronounced temperature dependency. The activation energy of thermal-quenching-induced PL emissions was estimated as 61.5 meV and 82.6 meV for WSe2 and MoS2, respectively. Additionally, we observed that the spectral full width at half maximum (FWHM) of Raman and PL peaks increases as the temperature increases, and these broadenings can be attributed to the phonon interaction and the expansion of the heterostructure's thermal coefficients. This work provides valuable insights into the interlayer coupling of van der Waals heterostructures, which is essential for understanding their potential applications in extreme temperatures.

Strain-induced ultrahigh power conversion efficiency in BP-MoSe2vdW heterostructure

Photocatalytic water splitting is a promising method for hydrogen production, and the search for efficient photocatalysts has received extensive attention. Two-dimensional van der Waals (vdW) heterostructures have recently been considered excellent candidates for photocatalytic water splitting. In this work, a BP-MoSe₂vdW heterostructure composed of a blue phosphorus (BP) and MoSe₂monolayer was studied as a potential photocatalyst for water splitting using first-principles calculations. The results show that the heterostructure has a type-II band structure, and the band edges straddle water redox potentials under biaxial strains from -3% to 2%, satisfying the requirements for photocatalytic water splitting. In addition, the heterostructure has excellent power conversion efficiency (PCE) and strong optical absorption in both visible light and near-ultraviolet region, indicating that it is a very promising candidate for photocatalytic water splitting. Specifically, the PCE was enhanced to ∼20.2% under a tensile strain of 2%. The Gibbs free energy profiles indicate that BP-MoSe₂vdW heterostructure exhibits good catalytic performance in hydrogen and oxygen evolution reactions. In particular, high carrier mobility implies that the transfer of carriers to reactive sites is easy, and the recombination probability of photogenerated electron-hole pairs is reduced.

Strain Effects on the Electronic and Optical Properties of Blue Phosphorene

Monolayer blue phosphorene (BlueP) systems were investigated under biaxial strain range from −10% to +10%. All these systems exhibit excellent stability, accompanying changes in the electronic and optical properties. BlueP becomes metallic at −10% strain and transforms into a direct semiconductor at 10% strain while maintaining indirect semiconductor behaviors at −8% to +8% strain. The bandgap of BlueP decreases linearly with strain, and tensile strain exhibits a more moderate bandgap modulation than compressive strain. The real part of the dielectric function of BlueP is enhanced under compressive strain, while the optical absorption in the visible and the infrared light regions increases significantly under tensile strain. The maximum absorption coefficient of 0.52 ×105/cm occurs at 530 nm with the 10% strain. Our analysis indicates that the semiconductor–metal transition and the indirect–direct bandgap transition are the competition results of the energy states near the Fermi level under a massive strain. The potent compressive strain leads the py orbitals of the conduction band to move downward and pass through the Fermi level at the K point. The robust tensile strain guides the energy states at the Γ point to approach the Fermi level and become the band edges. Our results suggest that the energy storage capacity of BlueP can be significantly improved by compressive strain, while the visible light photocatalytic performance is enhanced by tensile strains of less than 8%. Our works provide a reference for the practical applications of BlueP in photocatalyst, photovoltaic cells, and electronic devices.