The viability of novel coextruded, fluoropolymer-free backsheets for photovoltaic (PV) modules has been questioned as a result of a large number of early-life backsheet failures in PV installations containing one of the earliest co-extruded polyamide (PA)-based backsheet to reach the market, “AAA.” New PV reliability testing protocols have been recently developed and applied to backsheets to reproduce failures observed in the field and evaluate the durability of novel backsheet materials and designs prior to commercialization. A new co-extruded PA-based backsheet was tested using combined-accelerated stress testing (C-AST) and demonstrated a greater lifetime than AAA, and some other fluoropolymer-based backsheets such as polyvinylidene fluoride. The improved PA-based backsheet also eventually failed by through-thickness cracking. Using surface and bulk material characterization techniques, we performed a comprehensive study of material properties before and after the stress testing. Aging of the backsheet resulted in an increase of surface roughness by erosion of the outer PA layer. However the failure is more likely related to an increase in crystallinity of the polyolefin core layer reducing the backsheet tearing energy. The analysis can ultimately inform on the specific weaknesses of the materials so that the manufacturer can improve the backsheet design to extend its lifetime.

中文翻译：

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复合加速应力测试后新型聚酰胺基无氟聚合物背板的失效分析

用于光伏 (PV) 模块的新型共挤、不含氟聚合物背板的可行性受到质疑，因为在包含最早的共挤聚酰胺 (PA) 背板之一的光伏装置中，出现了大量早期背板故障打入市场，“AAA”。最近开发了新的光伏可靠性测试协议并应用于背板，以重现现场观察到的故障，并在商业化之前评估新型背板材料和设计的耐用性。使用联合加速应力测试 (C-AST) 对一种新型共挤 PA 基背板进行了测试，结果表明其使用寿命比 AAA 和其他一些含氟聚合物基背板（如聚偏二氟乙烯）更长。改进的基于 PA 的背板也最终因全厚度开裂而失效。使用表面和散装材料表征技术，我们对应力测试前后的材料特性进行了全面研究。背板的老化导致外 PA 层的侵蚀增加了表面粗糙度。然而，失效更可能与聚烯烃芯层结晶度的增加降低背板撕裂能有关。分析最终可以了解材料的具体弱点，以便制造商可以改进背板设计以延长其使用寿命。然而，失效更可能与聚烯烃芯层结晶度的增加降低背板撕裂能有关。分析最终可以了解材料的具体弱点，以便制造商可以改进背板设计以延长其使用寿命。然而，失效更可能与聚烯烃芯层结晶度的增加降低背板撕裂能有关。分析最终可以了解材料的具体弱点，以便制造商可以改进背板设计以延长其使用寿命。