Submicron Cu(In,Ga)Se₂ Solar Cells With Over 20% Efficiency Enabled by Novel Construction of U-Shape Ga-Gradient

Area of Science:

• Materials Science
• Renewable Energy
• Semiconductor Physics

Background:

• Submicron Copper Indium Gallium Selenide (CIGS) solar cells offer potential for reduced material usage and cost.
• Progress in efficiency has been limited by challenges in achieving optimal gallium (Ga) gradients in thin absorber layers.

Purpose of the Study:

• To develop a novel method for fabricating high-performance submicron CIGS solar cells.
• To engineer a specific U-shaped Ga gradient crucial for enhanced photovoltaic properties.

Main Methods:

• Exploited the Cu-Se phase to control Gallium/Indium interdiffusion.
• Fabricated submicron CIGS films with a U-shaped Ga double gradient.
• Maintained high film quality despite reduced absorber thickness.

Main Results:

• Achieved a U-shaped Ga double gradient in submicron CIGS films.
• Significantly boosted quantum efficiency in the near-infrared spectrum.
• Substantially reduced the open-circuit voltage deficit.
• Demonstrated over 20% efficiency with an absorber thickness of 935 nm.

Conclusions:

• The Cu-Se phase is critical for forming the Ga double gradient in ultrathin CIGS.
• This strategy enables high-performance ultrathin CIGS solar cells.
• Provides a valuable approach for bandgap engineering in other photovoltaic technologies.