Weathering Behavior of Colored Thermoplastic Encapsulants for Double-Glass Photovoltaic Modules

A promising technology for manufacturing of colored photovoltaic (PV) is the incorporation of interference pigments in the front encapsulant based on thermoplastic polyolefin (TPO). To ensure a high stability of color and efficiency during the life span of a PV module, artificial weathering is essential to assess potential ageing induced changes. The main objective of this work was to evaluate the effect of the interference pigments on the optical properties under weathering conditions. Therefore, double glass laminates were prepared and exposed to cyclic weathering, continuous irradiation and damp heat for 4000 h. An embossed and 8 non-embossed films were characterized by UV/Vis/NIR spectrometry. No negative interactions between the pigments and the encapsulant were ascertained. Whereas cyclic weathering and continuous irradiation led to changes in hemispheric transmittance and haze of less than 1 %, damp heat ageing had a more significant effect with a drop in hemispheric transmittance below 5 %. Interestingly, the laminate based on the embossed transparent (not-pigmented) encapsulant revealed a higher water uptake, a reduced hemispheric transmittance and an increased haze after damp heat exposure.