Photovoltaic module antireflection coating degradation survey using color microscopy and spectral reflectance

Journal Article · 05 June 2022 · Progress in Photovoltaics

DOI: https://doi.org/10.1002/pip.3575 · OSTI ID:1996044

Karin, Todd  ^[1]; Reed, Mason ^[2]; Rand, Jim ^[2]; Flottemesch, Robert ^[3]; Jain, Anubhav  ^[4]

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1. Lawrence Berkeley National Laboratory Berkeley USA, PV Evolution Labs Napa California USA
2. Core Energy Works Newark Delaware USA
3. Luminace New York City New York USA
4. Lawrence Berkeley National Laboratory Berkeley USA

Abstract Commercial antireflective coatings (ARCs) on photovoltaic (PV) module glass can improve module power by 2.5%–3.0%, but their long‐term field performance requires additional study. In this paper, we investigate ARC performance on fielded modules using two nondestructive techniques: reflectance spectroscopy and RGB microscopy, finding a large variation in coating durability and performance. For new coatings, the fleet average nominal power enhancement is 2.8%. This power enhancement is observed to degrade at approximately −0.05%/year absolute over the first 8 years of fielding in arrays that are not regularly cleaned. Interferometry and imaging results imply that coating loss for these modules is due to slow chemical thinning of the initial 125 nm thick coating by 1.4 to 5.0 nm/year. Due to the physics of interference coatings, the performance loss is projected to accelerate as the coating is further thinned, resulting in a coating lifetime (time to 80% of initial performance) of 7.5 to 25 years. At the higher 5.0 nm/year coating loss rates, we estimate that −0.14%/year power degradation of the module can be attributed solely to ARC degradation over the first 20 years. Extreme coating loss is observed on some modules where after 8 years fielding, the coating can be completely removed with a single wet wipe with a lens tissue. A case study is also presented comparing ARC and noncoated modules installed at a single site in 2013. We find that the ARC modules have a 2.6% higher soiling power loss than the noncoated modules; this exceeds the ARC power enhancement of 2.4% and leads to the surprising conclusion that the ARC lowers production for modules in this location due to increased soiling. These results demonstrate that RGB microscopy is a powerful, field‐capable, and quantitative characterization technique for assessing degradation of PV module ARCs.

• Sponsoring Organization: USDOE
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1996044
• Journal Information: Progress in Photovoltaics, Journal Name: Progress in Photovoltaics Journal Issue: 11 Vol. 30; ISSN 1062-7995
• Publisher: Wiley Blackwell (John Wiley & Sons)Copyright Statement
• Country of Publication: United Kingdom
• Language: English