Presentation Details
| Optical and chemical degradation mechanisms in modern encapsulant materials for UV-ID mitigation Dennice M.Roberts, Xavier Hanna, David C.Miller, Jimmy Newkirk, Kent Terwiliger, Rachael L.Arnold, Rebecca Wai, Peter Hacke, Dana Kern. National Laboratory of the Rockies, Golden, CO, USA |
Abstract
Modern Si photovoltaic modules with n-type cells provide high performance but are vulnerable to UV-induced degradation (UV-ID). Encapsulant choice can be used to mitigate UV-ID, but for this strategy to be effective the encapsulants themselves must be robust to UV illumination. This work studies the performance and durability of 14 commercial encapsulant products, including materials with EVA, POE, and EPE base polymers and a range of additive types that induce UV-transmitting (UV-T), UV-blocking (UV-B), and UV-downshifting (UV-DS) properties. Sample coupons are weathered in A3, A5, and UVA-340 conditions to study the effect of temperature, UV, and UV + visible light. We characterize the evolution of optical properties including transmittance, UV-cutoff, and yellowness index as a function of weathering time (0 to 4000 hours) and condition (A3, A5). We find that tracking changes in UV-range transmittance is a better metric for identifying changes to the performance of additives in encapsulants designed to mitigate UV-ID, particularly UV-B and UV-DS encapsulants. While many encapsulants prove robust in the tested aging conditions, we find some materials that have a significant breakdown in additive performance. Additionally, we also characterize chemical properties before and after aging to elucidate degradation mechanisms. Initial degradation rates for highly degrading materials will also be calculated.
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No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author.