Performance and durability of thin film solar cells via testing the abrasion resistance of broadband anti-reflection coatings

Abstract

Reflection from the front glass of solar modules causes over 4% optical loss leading to a significant decrease in module efficiency. Single layer solution gelation (sol-gel) anti-reflective (AR) coatings are effective over a narrow range of wavelengths, whereas reflection losses can be reduced over a broader wavelength when multilayer broadband AR coatings are applied. In this work, three different multilayer AR coatings including 4-layer SiO2/ZrO2, 4-layer SiO2/ITO, and 6-layer SiO2/ZrO2 were deposited using magnetron sputtering. The abrasion resistance is important because the coatings will be subject to regular cleaning cycles. A variety of abraders including Felt pad, CS-10 and CS-8 under different loads are used. The optical performance and durability of these coatings were analyzed using a spectrophotometer, optical microscope, scanning electron microscope, and scanning white light interferometer. No damage was observed after abrasion of the coatings with a felt pad under 1 and 2 N loads. However, there was a slight increase in Weighted Average Reflection. When coatings were tested with CS-10 and CS-8 abraders, coatings with ZrO2 resulted in higher scratch resistance in comparison to coating with ITO. However, all-dielectric broadband AR coatings are more durable and have better optical performance compared to single layer sol-gel coatings.