Six new silicon phases with direct band gaps

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Chemistry

Background:

• Diamond silicon, the most common allotrope, has an indirect band gap, limiting its efficiency in photovoltaic devices.
• Exploring new silicon phases with direct band gaps is crucial for developing advanced optoelectronic materials.

Purpose of the Study:

• To discover and characterize novel silicon phases with direct band gaps.
• To evaluate the stability and optoelectronic properties of these new silicon allotropes for potential photovoltaic applications.

Main Methods:

• High-throughput calculations were employed to substitute silicon atoms into known carbon structures.
• First-principles density functional theory (DFT) was used to systematically study crystal structures, stability, mechanical, electronic, and optical properties.

Main Results:

• Six new silicon phases were identified in space groups Im3[combining macron]m, C2/c, I4/mcm, I4/mmm, P21/m, and P4/mbm.
• All newly discovered phases are thermodynamically and mechanically stable at ambient pressure.
• These silicon allotropes possess direct band gaps ranging from 0.658 to 1.470 eV with excellent optoelectronic properties.

Conclusions:

• The six newly discovered silicon phases are stable and possess favorable electronic and optical properties.
• These silicon allotropes show significant promise as advanced materials for photovoltaic applications, potentially outperforming diamond silicon.