Microscopy Visualization of Carrier Transport in CdSeTe/CdTe Solar Cells.

Area of Science:

• Materials Science
• Solid-State Physics
• Photovoltaics

Background:

• Solar cells rely on minority carrier behavior, making carrier transport crucial for understanding their operation.
• Cadmium telluride (CdTe) solar cells are a key technology, but their complex transport mechanisms require further investigation.
• Inhomogeneous polycrystalline thin-film structures present challenges in analyzing charge carrier dynamics.

Purpose of the Study:

• To develop and apply a transport imaging technique for direct visualization of charge motion and collection in CdTe solar cells.
• To elucidate the influence of electric junctions, interfaces, recombination, and material composition on carrier transport.
• To understand cell operation and degradation mechanisms under stress conditions.

Main Methods:

• Development of an advanced transport imaging technique to directly visualize carrier motion.
• Application of the technique to state-of-the-art cadmium telluride solar cells.
• Integration of experimental findings with device modeling.

Main Results:

• Revealed complex, inhomogeneous carrier transport profiles in polycrystalline CdTe solar cells.
• Observed a unique dual peak in the carrier transport light intensity decay profile of pristine cells.
• Demonstrated the disappearance of this dual peak in degraded cells after light and heat stress, indicating degradation effects.

Conclusions:

• Selenium diffusion is identified as a significant factor influencing carrier transport in CdTe solar cells.
• The study provides a new method to correlate atomic/nanometer-scale properties with submicrometer optoelectronic behavior.
• This work bridges a critical knowledge gap in understanding solar cell physics and degradation.