Lone pair driven anisotropy in antimony chalcogenide semiconductors

Area of Science:

• Materials Science
• Condensed Matter Physics
• Renewable Energy

Background:

• Antimony sulfide (Sb₂S₃) and selenide (Sb₂Se₃) are earth-abundant thin-film photovoltaic materials.
• These materials exhibit anisotropic crystal structures with quasi-one-dimensional [Sb₄X₆] ribbons.
• Sb₂X₃ are typically classified as 1D semiconductors due to assumed van der Waals (vdW) inter-ribbon interactions.

Purpose of the Study:

• To investigate inter-ribbon interactions in Sb₂X₃ beyond the vdW regime.
• To elucidate the origin of structural anisotropy in Sb₂X₃.
• To analyze the impact of anisotropy on electronic, dielectric, and optical properties for photovoltaic applications.

Main Methods:

• First-principles calculations were employed to analyze electronic structures.
• Analysis focused on the stereochemical activity of the Sb 5s lone pair.
• Electronic, dielectric, and optical properties were examined in relation to structural anisotropy.

Main Results:

• Inter-ribbon interactions in Sb₂X₃ extend beyond the vdW regime.
• Structural anisotropy originates from the stereochemical activity of the Sb 5s lone pair.
• Anisotropy influences electronic properties, including higher-dimensional Fermi surfaces for charge transport.

Conclusions:

• Sb₂X₃ exhibit complex inter-ribbon interactions not solely explained by vdW forces.
• Understanding the role of the Sb 5s lone pair is crucial for explaining anisotropy.
• The findings offer guidelines for optimizing Sb₂X₃-based photovoltaics through device structuring that leverages crystal anisotropy.