ZnTiN₂ as an Electron-Selective, Protective Layer on Si Photocathodes

Area of Science:

• Materials Science
• Electrochemistry
• Renewable Energy

Background:

• Photoelectrochemical (PEC) fuel production demands robust photoelectrodes for efficient solar energy conversion.
• Carrier-selective interfaces are crucial for high photovoltage in photovoltaic devices.
• Semiconductor photoelectrodes require protective layers against degradation in aqueous environments.

Purpose of the Study:

• To investigate zinc titanium nitride (ZnTiN2) as an electron-selective and protective layer for silicon (Si)-based photocathodes.
• To evaluate the performance and stability of ZnTiN2/Si heterojunctions for PEC applications.
• To assess the protective capabilities of ZnTiN2 against degradation under various operational conditions.

Main Methods:

• Fabrication of ZnTiN2/p-type Si heterojunctions.
• Characterization of photovoltage and photocurrent under different pH and illumination conditions.
• Long-term stability testing in aqueous solutions (dark and illuminated).
• Surface analysis using elemental characterization techniques.

Main Results:

• ZnTiN2 formed a heterojunction with Si, facilitating electron transfer for reduction reactions.
• ZnTiN2/Si photocathodes achieved an open-circuit voltage of ~400 mV, outperforming bare Si under certain conditions.
• ZnTiN2 demonstrated significant protection against degradation, with minimal open-circuit voltage loss over 72 hours in dark and 21 hours under illumination.
• Surface oxides formed on ZnTiN2, consistent with Pourbaix diagrams, which enhanced durability without impeding charge extraction.

Conclusions:

• ZnTiN2 is a promising material for developing durable and efficient electron-selective layers in Si-based photocathodes.
• The co-design of carrier-selective and protective layers is vital for advancing PEC fuel production.
• ZnTiN2 offers a viable solution for enhancing the stability and performance of photoelectrochemical systems.