Absolute Reflectance Measurement of Anti-Reflective Film for Solar Cells Using the SolidSpec-3700

Significance of the Topic

Solar cells convert light into electricity, and anti-reflective (AR) coatings play a key role in maximizing photon absorption by minimizing surface losses. Measuring the absolute reflectance of AR films is critical to assess coating performance and optimize cell efficiency.

Study Objectives and Overview

The study focused on quantifying the absolute reflectance of a silicon nitride AR layer deposited on silicon wafers representative of photovoltaic cells. A UV-VIS-NIR spectrophotometer equipped with a variable-angle reflectance module enabled assessment across multiple incidence angles and polarization states.

Methodology

Reflectance measurements were performed at incidence angles of 5°, 15°, 30°, 45° and 60° for both s- and p-polarized light. Spectral data covered 300 to 2000 nm with 1 nm resolution at medium scan speed. Optical settings included a 32 nm slit, lamp switching at 310 nm, grating change at 720 nm and detector transitions at 870 nm and 1650 nm.

Used Instrumentation

• Shimadzu SolidSpec-3700 UV-VIS-NIR spectrophotometer
• Variable-angle absolute reflectance attachment
• Silicon wafer samples coated with silicon nitride AR film

Main Results and Discussion

Measured spectra revealed pronounced reflectance suppression in the visible region, with minimum values near 0.2% at 575 nm under s-polarization at 5° and 15° incidence. Data indicate that near-normal illumination yields optimal AR performance, while higher angles increase reflectance. Polarization effects were also characterized, confirming the film’s efficacy in reducing both s- and p-polarized reflections.

Benefits and Practical Applications

• Provides quantitative evaluation of AR coatings for photovoltaic optimization
• Supports process development, quality control and coating uniformity assessment
• Enables polarization-resolved analysis for advanced film design

Future Trends and Potential Applications

• Integration of in situ reflectance monitoring during film deposition
• Extension to multi-layer and gradient AR structures for broader spectral control
• Application in production-line inspection and long-term reliability testing

Conclusion

The absolute reflectance methodology using a variable-angle UV-VIS-NIR spectrophotometer offers a robust approach to characterizing AR films. The low reflectance values observed demonstrate the effectiveness of silicon nitride coatings in enhancing solar cell light capture under near-normal incidence.

References

• Shimadzu Application News No. A390: Variable-angle absolute reflectance attachment details
• Shimadzu Application News No. A394: Polarization measurement principles