Chemical depth profiling of photovoltaic backsheets after accelerated laboratory weathering

Abstract

Polymeric multilayer backsheets provide protection for the backside of photovoltaic (PV) module from the damage of moisture and ultraviolet (UV). Due to the nature of multilayer films, certain material property characterization of a backsheet could only be studied by examining its cross-section parallel to the thickness direction of the film. In this study, commercial PPE (polyethylene terephthalate (PET)/PET/ethylene vinyl acetate (EVA)) backsheet films were aged on the NIST (National Institute of Standards and Technology) SPHERE (Simulated Photodegradation via High Energy Radiant Exposure) with UV irradiance at 170 W/m 2 (300 nm to 400 nm) under accelerated weathering conditions of 85°C and two relative humidity (R.H.) levels of 5% (low) and 60% (high). Cryo-microtomy was used to obtain crosssectional PPE samples with a flat surface parallel to the thickness direction, and chemical depth profiling of multilayers was conducted by Raman microscopic mapping. Atomic force microscopy with peak force tapping mode was used complementarily for cross-sectional imaging. The results revealed that the PPE backsheet films were comprised of five main layers, including pigmented-PET, core PET, inner EVA, pigmented-EVA and outer EVA, along with their interfacial regions and two adhesive layers. UV and moisture degradation on the outer pigmented PET layer was clearly observed; while the damage on the core PET layer was less significance, indicating that the outer pigmented PET layer effectively reduced the damage from UV. In high R.H. exposure, both adhesive layers were severely deteriorated. It was found that the EVA layers were susceptible to moisture at elevated temperature, especially for the pigmented-EVA. Based on the results of accelerated weathering, this depth profiling study brings new understanding to the mechanisms of failure observed in polymeric multilayer backsheets during field exposure.

Ag nanoparticles-based antimicrobial polycotton fabrics to prevent the transmission and spread of SARS-CoV-2

“…[41,42] It is also possible to observe in 1730 cm -1 the stretching of the C=O bonds of the esters and the stretching of the CH bonds of the methyl groups external to the ring, in 2975 cm -1 . [41][42][43] It is observed that the addition of Ag-based antimicrobials do not cause significant changes in the polycotton structure at short-range. As a complementary analysis to micro Raman spectroscopy, FTIR measurements were performed to investigate the functional groups of products after the incorporation of the two Ag-based antimicrobial solutions into the polycotton ( Figure 2).…”

Extraction and analysis of back-sheet layer from waste silicon solar modules

“…The 1316 cm −1 band corresponds to C-CH and O-CH bending. PET back-sheets have main characteristics bands at 1144 cm −1 , 1031 cm −1 , and 978 cm −1 due to mixed-mode (glycol C-O stretch + ring CH in-plane bend), mixed-mode (ring CH in-plane bend + COC + glycol C-O stretch, C-C stretch +CCO bending), and mixed-mode (O-CH2 stretch + glycol C-C stretch +ring torsion), respectively [28]. The Raman spectra show no significant difference in the extracted back-sheet compared to the reference PET back-sheet, which is also confirmed by FTIR.…”

Effect of thermo-mechanical ageing on materials and interface properties in flexible microelectronic devices

“…The Raman spectra of the PET substrate before and after 500h at 120°C are presented in Figure 7. The initial spectrum exhibits the conventional vibration bands of PET [26,27]. There was no spectral modification after thermal ageing.…”