Crystalline TiO₂ protective layer with graded oxygen defects for efficient and stable silicon-based photocathode

Area of Science:

• Materials Science
• Electrochemistry
• Renewable Energy

Background:

• Silicon-based photoelectrochemical devices face challenges balancing efficiency and long-term stability.
• This trade-off limits their practical application in areas like solar fuel production.

Purpose of the Study:

• To decouple the efficiency-stability trade-off in silicon-based photocathodes.
• To develop a facile method for enhancing photocathode performance.

Main Methods:

• Employing crystalline titanium dioxide (TiO2) with graded oxygen defects as a protective layer.
• Fabricating silicon-based photocathodes with this engineered TiO2 layer.
• Evaluating photocathode performance in a 1.0 M NaOH electrolyte.

Main Results:

• The crystalline TiO2 layer with oxygen defects enhanced stability and carrier transport.
• The silicon-based photocathode with black TiO2 achieved a limiting current density of ~35.3 mA cm⁻².
• The device demonstrated durability exceeding 100 hours at 10 mA cm⁻².
• A standard crystalline TiO2 layer without defects showed no photoelectrochemical activity.

Conclusions:

• Graded oxygen defects in crystalline TiO2 effectively decouple efficiency and stability in silicon photocathodes.
• This approach offers a pathway for highly efficient and durable photoelectrochemical devices.
• The findings are applicable to silicon-based, III-V compounds, and other photoelectrode materials.