Understanding of thedurability of each individual layer and their interfaces in a multilayered photovoltaic (PV)backsheetis critical to the design and selection of materials for making reliable andhigh performance PV modules. In this study, Raman imaging was used to depth profile the chemical degradation of a multilayer commercial backsheetfilm exposed to ultraviolet (UV) radiationat 85°C, 5% relative humidity (RH, dry) and 85°C,60% RH (humid)on the NIST (National Institute of Standards and Technology) SPHERE(Simulated Photodegradation via High Energy Radiant Exposure).The backsheetfilm wasa multipartlaminate comprising of a pigmented polyethylene terephthalate (PET)-based outer layer, PET core layer and three ethylene vinyl acetate (EVA) layers having different vinyl acetate(VA) contents, along with two inner adhesive layers between PET outer and PET core layers, and PET core and EVA layers. Cross-sectional samples were prepared by cryo-microtomyfor various characterizations.The multilayer structureswere examined by laser scanning confocal andatomic force microscopies, while their chemical degradation profiles were obtained by Raman spectroscopic imaging. Non-uniform degradation was observed in the agedbacksheet film, and both UV and moisture appeared tosignificantly affect the degradation profiles of the multilayers.Severe degradation, indicated by high fluorescence,occurredin the outermost region of the pigmented PET outer layer, and the degradation gradient extended to approximately 20 µm to the bulk. It was also found thattheinner adhesive layerswere severelydeterioratedunder moist condition, indicating thatthe long-termadhesion between the layers could be a major area of concern for multilayer backsheets used in a humid environment. The relationship between the sharp 3 (non-uniform) degradation profile, resultant internal stress, and ultimate failures (cracking and delamination)was discussed as well.