Non-destructive Characterization of Anti-Reflective Coatings on PV Modules

TL;DR

This paper presents a fast, accurate, and non-destructive method using a modified integrating-sphere probe to measure and analyze the spectral reflectance of anti-reflective coatings on solar PV modules in outdoor conditions.

Contribution

It introduces a novel interferometric model and measurement technique for in-field assessment of ARC degradation on PV modules.

Findings

Successful outdoor measurement of ARC spectral reflectance

Estimation of coating porosity, thickness, and coverage

Identification of ARC presence on active PV modules

Abstract

Anti-reflective coatings (ARCs) are used on the vast majority of solar photovoltaic (PV) modules to increase power production. However, ARC longevity can vary from less than 1 year to over 15 years depending on coating quality and deployment conditions. A technique that can quantify ARC degradation non-destructively on commercial modules would be useful both for in-field diagnostics and accelerated aging tests. In this paper, we demonstrate that accurate measurements of ARC spectral reflectance can be performed using a modified commercially-available integrating-sphere probe. The measurement is fast, accurate, non-destructive and can be performed outdoors in full-sun conditions. We develop an interferometric model that estimates coating porosity, thickness and fractional area coverage from the measured reflectance spectrum for a uniform single-layer coating. We demonstrate the measurement outdoors on an active PV installation, identify the presence of an ARC and estimate the properties of the coating.