Polarization-dependent angular-optical reflectance in solar-selective SnOx:F/Al2O3/Al reflector surfaces

Area of Science:

• Materials Science
• Optical Engineering
• Surface Science

Background:

• Spectrally selective surfaces are crucial for efficient solar energy conversion.
• Fluorine-doped tin oxide (SnOx:F) offers tunable optical properties.
• Anodized aluminum provides a robust substrate for thin film deposition.

Purpose of the Study:

• To investigate the polarization-dependent angular-optical properties of SnOx:F/Al reflector surfaces.
• To evaluate the spectral selectivity and angular behavior for solar cell applications.
• To correlate film thickness and polarization effects with reflectance characteristics.

Main Methods:

• Deposition of SnOx:F films pyrolytically on electrochemically produced anodic aluminum oxide (Al2O3) layers.
• Angular-reflectance measurements using s- and p-polarized light across the solar spectrum (0.3-2.5 microm).
• Variation of Al2O3 layer thickness (100-205 nm) and SnOx:F film thickness (180-320 nm).

Main Results:

• Strong spectral selectivity observed, with high reflectance below 1.1 microm and low thermal reflectance above 1.1 microm.
• Angular behavior strongly dependent on incident beam polarization, total film thickness, and individual layer thicknesses.
• Best samples achieved reflectance values of 0.80 (solar) and 0.42 (thermal) at near-normal incidence with a 155 nm anodic layer.
• Cell reflectance remained largely insensitive to incidence angle up to approximately 60 degrees.

Conclusions:

• SnOx:F/Al surfaces demonstrate excellent spectrally selective reflector characteristics for silicon solar cells.
• Optimized film thicknesses and electrochemical anodization enable high performance.
• The angular insensitivity of reflectance up to 60 degrees enhances practical applicability in solar devices.