Visualizing localized, radiative defects in GaAs solar cells.

Area of Science:

• Materials Science
• Solid State Physics
• Semiconductor Devices

Background:

• Gallium arsenide (GaAs) solar cells are crucial for high-efficiency energy conversion.
• Understanding defect-related luminescence is key to optimizing solar cell performance.
• Rear-junction architectures offer advantages in GaAs solar cell design.

Purpose of the Study:

• To investigate localized defects in high growth-rate, rear-junction GaAs solar cells using hyperspectral imaging.
• To characterize the photoluminescence (PL) emission from these defects across a temperature range.
• To correlate PL findings with solar cell device parameters.

Main Methods:

• Utilized a calibrated, wide-field hyperspectral imaging instrument for spectrally and spatially resolved PL imaging.
• Acquired data from 300 K down to 77 K.
• Analyzed temperature-dependent PL spectra and intensities.

Main Results:

• Observed a novel, double-peak luminescence emission at localized defect sites.
• Identified peaks corresponding to band-to-band and band-to-impurity transitions.
• Demonstrated that temperature-dependent PL evolution aligns with a free-to-bound recombination model involving a deep impurity center, likely a gallium antisite defect.
• Found agreement between PL modeling and external device parameters like open-circuit voltage.

Conclusions:

• The study successfully characterized defect-related luminescence in GaAs solar cells.
• A deep impurity center, potentially a gallium antisite defect, significantly influences the observed PL.
• The findings provide insights into the correlation between material defects and solar cell performance.