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High-Throughput Optical Mapping for Accelerated Stress Testing of Photovoltaic Module Materials

DuraMAT will develop a spectroscopy capability that will enable automated measurements of photovoltaic (PV) arrays of coupons as well as spatial mapping within a coupon.

In addition, the switch from a scanning spectrophotometer with a point detector (which measures one wavelength at a time) to CCD array-based spectrometers (which measure the full spectrum simultaneously) will reduce the measurement time from the present rate of 6 minutes per specimen. All the measured spectra will also be automatically analyzed and made available via the DuraMAT DataHub.

Testing of coupon specimens (e.g., sheet material, laminated glass/polymer/glass, etc.) is an established method to evaluate a wide variety of PV packaging materials for purposes including screening and degradation rate modeling. In practice, many coupons can be simultaneously aged in outdoor or accelerated testing. However, for optical performance characterization (hemispherical transmittance or reflectance), the coupons are presently measured one at a time using a commercial spectrophotometer. This slow and labor-intensive measurement process limits the scope and size of coupon studies and further, usually only the center of the coupon is measured. However, prior studies show that degradation and consequent material damage are often spatially distributed as a function of water- and oxygen-ingress with the size of the affected region being material (formulation) dependent.

Core Objective

Disruptive Acceleration Science


National Renewable Energy Laboratory


This novel instrument enables rapid optical characterization of material, coupon, or mini-module specimens: 

  • Characterize samples before and after aging
  • Optical mapping within specimens. 


Available to collaborators at national labs and industry.


David C. Miller, Jayesh G. Bokria, David M. Burns, Sean Fowler, Xiaohong Gu, Peter L. Hacke, Christian C. Honeker, Michael D. Kempe, Michael Köhl, Nancy H. Phillips, Kurt P. Scott, Ashish Singh, Shigeo Suga, Shin Watanabe, Allen F. Zielnik, “Degradation in Photovoltaic Encapsulant Transmittance: Results of the First PVQAT TG5 Study”, Progress in Photovoltaics: Research and Applications, 27 (5) 2019, 391-409. 

David C. Miller, Asher Einhorn, Clare L. Lanaghan, Jimmy Newkirk, Bobby To, Helio R. Moutinho, Paul F. Ndione, Jim J. John, Lin J. Simpson, Chaiwat Engtrakul, “The Abrasion of Photovoltaic Glass: A Comparison of the Effects of Natural and Artificial Aging”, IEEE Journal of  Photovoltaics, 10 (1), 2020, 173-180 

David C. Miller, Hussameldin I. Khonkar, Rebeca Herrero, Ignacio Antón, David K. Johnson, Thorsten Hornung, Tobias Schmid- Schirling, Todd B. Vinzant, Bobby To, Gabriel Sala, and Sarah R. Kurtz, “An End of Service Life Assessment of PMMA Lenses from Veteran Concentrator Photovoltaic Systems”, SOLMAT, 167, 2017, 7-21. 

Jimmy M. Newkirk, Illya Nayshevsky, Archana Sinha, Adam Law, QianFeng Xu, Bobby To, Paul F. Ndione, Laura T. Schelhas, John M. Walls, Alan M. Lyons, David C. Miller, “Artificial linear brush abrasion of coatings for photovoltaic module first-surfaces”, Solar Energy Materials and Solar Cells, Proc. International Soiling Workshop, 2019.


To learn more about this project, contact David Miller.

Three optical heat mapping graphs and an image of a coupon showings its length at 2 cm

Optical mapping of a glass/EVA/glass coupon after xenon weathering. The instrument capability allows for spatial quantification of the: (a) optical transmittance [PV device representative, solar weighted]; (b) UV cut-off wavelength; and (c) yellowness index (discoloration).