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Degradation Mechanisms and the Role of Sequenced Accelerated Testing to Ensure Long-Term Solar Module Encapsulation

DuraMAT will develop and experimentally validate a science-based encapsulant degradation rate model for accurate material and interfacial property evaluation over extended exposures for lon (50-year) photovoltaic (PV) module lifetimes.

Current lifetime models are often not based on actual chemical/molecular degradation mechanisms and do not capture the interaction of degradation processes that are known to lead to auto-catalytic effects where one reaction pathway may accelerate another, leading to significant challenges in designing sequences using preconditioning and accelerated aging. For example, the same set of separate steady-state aging tests may give different results if the tests are applied in a different order.

This project aims to understand the fundamental mechanisms and their interactions and incorporate lessons learned into designing accelerated testing strategies using sequenced exposures, more accurate lifetime predictions, and packaging design strategies including innovative bifacial, glass/glass, and lightweight flexible all-polymer modules. Our project goals include leveraging our Stanford University and National Renewable Energy Laboratory (NREL) teams high-resolution experimental and modeling capabilities to achieve these goals in a 2- year program contributing directly to DuraMAT’s core objectives.

Core Objective

Disruptive Acceleration Science


Stanford University and NREL


The rate models may be subsequently used to predict performance degradation or service life. The optimum sequence of steady-state tests identified may be used for more rapid and robust screening of legacy and emerging PV packaging materials.


Available to NREL scientists and external collaborators.


[1] Liu, A.; Thornton, P.; Dauskardt, R.H. Predictive Fracture Mechanics and Photochemical Reaction Kinetics Modeling of the Reliability of Silicon Photovoltaic Modules with Polymeric Encapsulants Undergoing Field Aging. In preparation.

[2] Tracy, J., D’hooge, D. R., Bosco, N., Delgado, C. & Dauskardt, R. Evaluating and predicting molecular mechanisms of adhesive degradation during field and accelerated aging of photovoltaic modules. Prog. Photovoltaics Res. Appl. 26, 981–993 (2018).

[3] Thornton, P.; Moffitt, S. L.; Schelhas, L. T.; Dauskardt, R. H. Dependence of Adhesion on Degradation Mechanisms of Ethylene Co-Vinyl Acetate Encapsulants over the Lifetime of Photovoltaic Modules. Solar Energy Materials and Solar Cells 2022, 244, 111818.


To learn more about this project, contact Alan Liu, Reinhold Dauskardt, David Miller, or Nick Bosco.

Diagrams showing degradation mechanisms, accelerated test sequences, characterization, and predictive modeling.

Degradation mechanisms are directly quantified and compared to the results of accelerated test sequences. Material-specific and coupons specimens will be used to develop and validate a degradation rate model for interfacial adhesion.