MoSe₂ is a promising candidate for tunable near-infrared photodetectors owing to its band gap alignment with optical fiber communication windows. We combine diamond anvil cell techniques with density functional theory calculations to investigate pressure-induced structural evolution and optoelectronic modulation in MoSe₂. X-ray diffraction and Raman spectroscopy confirm that the hexagonal 2H phase remains stable up to 10 GPa, exhibiting pronounced anisotropic compression. The c-axis compressibility is approximately three times that of the a-axis. Infrared reflectivity spectra show a monotonic increase in reflectance with pressure, indicating a bandgap narrowing trend. First-principles calculations reveal a pressure-driven downward shift of the conduction band minimum, with the band gap narrowing linearly from 1.24 eV at ambient pressure to 0.77 eV at 4 GPa and optical absorption being enhanced. Photocurrent increases progressively from 0.4 to 3.9 GPa, peaking at approximately twice the ambient value before vanishing at 4.3 GPa due to overwhelming dark current. The consistency between theoretical predictions and experimental observations elucidates the electronic origin of the pressure-tuned optoelectronic response, providing a foundation for MoSe₂-based pressure-modulated spectral devices.

Polyvinylidene fluoride (PVDF) is a versatile semi-crystalline polymer exhibiting outstanding piezoelectric, pyroelectric and dielectric properties, and is therefore widely employed in sensors, energy devices and biomedical applications. Its performance is governed by crystallinity and the polymorphic constitutiona (α, β, γ, δ, ε), among which the polar β-phase possesses superior electromechanical characteristics compared with the non-polar α-phase. Nevertheless, the α-phase remains the most stable and the most readily obtained thermodynamical form. The structural evolution of PVDF under high pressure is investigated by means of in situ X-ray diffraction and Fourier-transform infrared spectroscopy. At ambient conditions the powder consists primarily of the α-phase with a minor fraction of β. Upon compression to 0–20 GPa, the α phase gradually diminishes; the emergence of new diffraction peaks and band shifts indicates sequential α→β and β→γ transformations, accompanied by a pronounced increase in β content and concomitant formation of γ. When the pressure exceeds 20 GPa, severe lattice distortion destroys long-range crystalline order, resulting in peak broadening and eventual amorphization. The study unveils the intricate interplay between pressure-induced chain rearrangement and polymorphic transitions, clarifies the high-pressure phase-transformation pathway and structural evolution of PVDF, and thereby deepens the structure–property understanding of this polymer. The findings also provide a theoretical basis for tailoring its performance under extreme conditions and for designing high-pressure technologies.