Surface photogalvanic effect in Ag₂Te

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• The bulk photovoltaic effect (BPVE) in non-centrosymmetric materials offers potential beyond the Shockley-Queisser limit.
• Artificial symmetry reduction has been explored to induce BPVE in wider material systems, but faces implementation challenges.
• Centrosymmetric materials typically do not exhibit BPVE, limiting the scope of photovoltaic material discovery.

Purpose of the Study:

• To investigate the potential for photocurrent generation in centrosymmetric topological insulator silver telluride (Ag₂Te).
• To attribute the observed photocurrent to a specific mechanism, namely the surface photogalvanic effect (SPGE).
• To explore the feasibility of Ag₂Te as a material for advanced photovoltaic applications.

Main Methods:

• Fabrication of specially designed devices using Ag₂Te.
• Spatially-resolved measurements to probe photocurrent generation.
• Analysis of photocurrent origin by examining contributions from top and bottom surfaces.

Main Results:

• Demonstrated a large intrinsic photocurrent response in centrosymmetric Ag₂Te.
• Attributed the photocurrent to the surface photogalvanic effect (SPGE) induced by surface symmetry reduction.
• Observed that SPGE arises from the differential photocurrents generated from the top and bottom surfaces of Ag₂Te.
• Ag₂Te exhibited robust performance across a broad spectral range (visible to mid-infrared).

Conclusions:

• Ag₂Te is an efficient SPGE material, overcoming the symmetry constraints of traditional BPVE materials.
• The findings suggest SPGE can be generated on low-symmetry surfaces in various systems, expanding photovoltaic material choices.
• Ag₂Te shows promise for applications in solar cells and mid-infrared detectors.