Degradation in photovoltaic encapsulant transmittance: Results of the second PVQAT TG5 artificial weathering study

The optical degradation of encapsulants from ultraviolet (UV) radiation has historically resulted in a significant loss performance throughout the life photovoltaic (PV) module. International Electrotechnical Commission (IEC) test methods have recently been developed to screen for PV prone performance. present study was performed benchmark polymeric packaging materials relative IEC 62788-1-4 (covering measurement transmittance) and 62788-1-7 (on durability transmittance), provide feedback toward improvement methods, develop insight regarding degradation. Contemporary were examined, including poly(ethylene-co-vinyl acetate) (EVA), thermoplastic polyolefin (TPO), elastomer (POE), polyvinyl butyral (PVB) encapsulants; poly(ethene-co-tetrafluoroethene)/poly(ethylene terephthalate) (ETFE/PET) transparent backsheet; polystyrene (PS) working reference material. use silica-, specialty-, rolled-glass also compared laminated coupons. Specimen size separately examined 2.5 12.5 cm. Weathering with xenon source, using TS 62788-7-2 A2, A3, A4, A5 (chamber temperature 55°C, 65°C, 75°C, or 85°C), respectively. Characterizations made UV–visible–near-infrared (UV–VIS–NIR) spectrophotometer (transmittance reflectance, without an integrating sphere), UV–VIS fluorescence spectrophotometer, camera, microscope. Performance analyzed, solar weighted transmittance, yellowness index, UV cut-off wavelength, haze (scattering). Separate Arrhenius analyses assess retention transmittance changes index. activation energy both characteristics found range 15–80 kJ·mol−1, average 48 similar 45 kJ·mol−1 identified previous international Quality Assurance Task Force (PVQAT) Group 5 (TG5) more traditional encapsulants. separate modes discoloration scattering distinguished comprehensive spectral characterization. Based on these results, pass/fail criteria 5% change confirmed identify known bad encapsulant.