A highly efficient Cu(In,Ga)(S,Se)₂ photocathode without a hetero-materials overlayer for solar-hydrogen production

Area of Science:

• Materials Science
• Photovoltaics
• Electrochemistry

Background:

• Surface modification of copper indium gallium selenide sulfide (CIGSSe) absorber layers is standard for high-performance photocathodes.
• Traditional surface modifications can lead to optical losses, reduced stability, toxicity, and increased complexity.

Purpose of the Study:

• To demonstrate a double-graded bandgap structure in bare CIGSSe photocathodes to achieve high performance without surface modification.
• To develop a cost-effective solution process for fabricating these modified CIGSSe photocathodes.

Main Methods:

• Fabrication of CIGSSe films using two distinct precursor solutions with varying solvents and binders.
• Characterization of the resulting double-graded bandgap structure (S-rich top, Ga- and S-poor middle, S- and Ga-rich bottom).
• Evaluation of photoelectrochemical (PEC) activity of bare CIGSSe photocathodes and those with a platinum (Pt) catalyst.

Main Results:

• The CIGSSe films naturally exhibited a double-graded bandgap structure.
• Bare CIGSSe photocathodes showed significant PEC activity (~6–22 mA·cm⁻²).
• Incorporation of a Pt catalyst further enhanced PEC activity (~26 mA·cm⁻²).

Conclusions:

• A double-graded bandgap structure in bare CIGSSe photocathodes eliminates the need for surface modifications.
• Cost-effective solution processing enables the fabrication of high-performance, stable, and less complex CIGSSe photocathodes.
• This approach offers a promising pathway for advanced photovoltaic and photoelectrochemical applications.