Intense photocurrent from Mo-doped TiO2 film with depletion layer array

Area of Science:

• Materials Science
• Photovoltaics
• Semiconductor Physics

Background:

• Titanium dioxide (TiO2) is a widely studied semiconductor for photocatalytic and photovoltaic applications.
• Enhancing photocurrent generation under visible light is crucial for efficient solar energy conversion.
• Developing novel nanostructures can improve charge carrier dynamics in TiO2 films.

Purpose of the Study:

• To investigate a novel bilayer TiO2 film structure for enhanced visible-light photocurrent.
• To explore the impact of a deposition-etching-redeposition process on TiO2 film properties.
• To correlate microstructural modifications with photocurrent performance.

Main Methods:

• Fabrication of a bilayer TiO2 film with a Mo-doped etched base layer and an undoped surface layer.
• Characterization using scanning electron microscopy, atomic force microscopy, X-ray diffraction, and UV-Vis spectroscopy.
• Measurement of photocurrent density under visible light using an electrochemical workstation.

Main Results:

• The novel structure successfully created an array of depletion layers within the TiO2 film.
• High parallel diffusivity near the depletion layer significantly enhanced carrier collection probability.
• Photocurrent density increased with etching depth, achieving a 56-fold enhancement at 660 nm etching depth compared to a standard TiO2 film.
• Visible light response was significantly improved.

Conclusions:

• The developed bilayer TiO2 structure with embedded depletion layers is highly effective for boosting visible-light photocurrent.
• The etching process and resulting trench structures are key to improved carrier collection and photocurrent.
• The concept of depletion layers at trench edges holds significant potential for optimizing wide-bandgap semiconductor films.