Local photocurrent mapping and cell performance behaviour on a nanometre scale for monolithically interconnected...

Area of Science:

• Materials Science
• Renewable Energy
• Nanotechnology

Background:

• Lamellar shaped copper indium gallium selenide (Cu(In,Ga)Se2) solar cells are a key area of research in renewable energy.
• Understanding local efficiency variations is crucial for optimizing photovoltaic device performance.

Purpose of the Study:

• To investigate the local efficiency of lamellar Cu(In,Ga)Se2 solar cells at the nanoscale.
• To correlate photocurrent generation with surface topography and material properties.

Main Methods:

• Simultaneous topographic and photocurrent measurements using scanning near-field optical microscopy (SNOM).
• Utilized a 100 nm tip aperture for high-resolution nanoscale analysis.
• Investigated different regions of a P-scribed lamellar solar cell.

Main Results:

• The cell region between P1 and P2 significantly contributes to overall photocurrent generation.
• Photocurrent is dependent on local sample topography, primarily due to roughness variations in the ZnO:Al/i-ZnO top electrode.
• Regions under large ZnO grains produced less current compared to regions under small granules.
• Observed photocurrent features were attributed to the ZnO:Al/i-ZnO top electrode and were independent of light wavelength (532 nm and 633 nm).

Conclusions:

• Local topography of the ZnO:Al/i-ZnO electrode significantly impacts photocurrent generation in lamellar Cu(In,Ga)Se2 solar cells.
• Nanoscale characterization using SNOM provides critical insights into efficiency variations.
• Optimization of electrode surface morphology is essential for enhancing solar cell performance.