Poly(ethylene-terephthalate) (PET) film is widely used in photovoltaic module backsheets, for its dielectric breakdown strength, and in applications requiring high optical clarity. PET degrades under exposure to ultraviolet (UV) irradiance, heat, and moisture, which leads to loss of optical clarity and performance properties. To study the weathering driven degradation of PET films, three grades of PET, including unstabilized and stabilized grades, were exposed to three types of accelerated weathering exposure. Fluorescence excitation-emission matrix (EEM) spectra were collected after predetermined exposure intervals. Parallel factor analysis (PARAFAC) was applied to the resulting spectra to decompose the fluorescence data into individual fluorophore components and monitor their relative concentrations over time. EEM-PARAFAC was used to identify and distinguish between the formation of monohydroxy-terephthalate and dihydroxy-terephthalate units in PET over time under the UV-light bearing accelerated exposures. The relative concentrations of these fluorophores were found to increase, while the relative concentration of the PARAFAC component assigned to PET was found to generally decrease. ATR-FTIR was used to support findings from EEM-PARAFAC. Results were also used to assess the impact of additives (UV stabilizer and TiO₂) on degradation.

聚对苯二甲酸乙二酯（PET）膜因其介电击穿强度而被广泛用于光伏模块背板，以及需要高光学透明度的应用中。PET在暴露于紫外线（UV），热和湿气下会降解，这会导致光学清晰度和性能下降。为了研究风化驱动的PET薄膜的降解，将三种等级的PET（包括不稳定和稳定级）暴露于三种类型的加速风化暴露下。在预定的曝光间隔后收集荧光激发-发射矩阵（EEM）光谱。将平行因子分析（PARAFAC）应用于所得光谱，以将荧光数据分解为单个荧光团成分，并随时间监视其相对浓度。EEM-PARAFAC用于识别和区分在紫外线加速照射下，PET中单羟基对苯二甲酸酯和二羟基对苯二甲酸酯单元的形成。发现这些荧光团的相对浓度增加，而发现分配给PET的PARAFAC组分的相对浓度通常降低。ATR-FTIR用于支持EEM-PARAFAC的发现。结果还用于评估添加剂（紫外线稳定剂和二氧化钛）的影响。而分配给PET的PARAFAC组分的相对浓度通常会降低。ATR-FTIR用于支持EEM-PARAFAC的发现。结果还用于评估添加剂（紫外线稳定剂和二氧化钛）的影响。而分配给PET的PARAFAC组分的相对浓度通常会降低。ATR-FTIR用于支持EEM-PARAFAC的发现。结果还用于评估添加剂（紫外线稳定剂和二氧化钛）的影响。₂）降解。