Encapsulation is a well-known impact factor on the durability of Photovoltaics (PV) modules. Currently there is a lack of understanding on the relationship between lamination process and module durability. In this paper, the effects of different lamination parameters on the encapsulant stability due to stress testing have been investigated from both on-site production quality and long-term stability viewpoints. Rather than focusing on single stability factors, this paper evaluates lamination stability using a number of indicators including EVA (ethylene-vinyl acetate copolymer) curing level, voids generation, chemical stability, optical stability, and adhesion strength. The influences of EVA curing level on the stability of other properties are also discussed. It is shown that laminates stability increases with increasing curing level to an upper limit, beyond which leading to the formation of voids, reduced transmittance stability, discoloration, and unstable interfaces. A minimum gel content is identified but an upper limit should not be surpassed. The best range of gel content for the materials tested here is 84–90%. Samples with gel content below 70% show low chemical and optical stability, weak adhesion strength, and EVA flowing. Laminates with gel content over 92% are more likely to become yellow and are less stable in adhesion.

Previous work on probing the dynamics of reptating polymer chains in terms of the segmental orientation autocorrelation function (OACF) by multiple-quantum (MQ) NMR relied on the time-temperature superposition (TTS) principle as applied to normalized double-quantum (DQ) build-up curves. Alternatively, an initial-rise analysis of the latter is also possible. These approaches are subject to uncertainties related to the relevant segmental shift factor or parasitic signals and inhomogeneities distorting the build-up at short times, respectively. Here, we present a simple analytical fitting approach based upon a power-law model of the OACF, by the way of which an effective power-law time scaling exponent and the amplitude of the OACF can be estimated from MQ NMR data at any given temperature. This obviates the use of TTS and provides a robust and independent probe of the shape of the OACF. The approach is validated by application to polymer melts of variable molecular weight as well as elastomers. We anticipate a wide range of applications, including the study of physical networks with labile junctions.

The reliability of solar modules is largely determined by the encapsulation materials used and their inherent additive composition. Although the use of polymer additives generally leads to better encapsulant characteristics, the diffusion of these species must be considered. While UV additives protect the encapsulant from photo degradation, their interactions with other additives or with formed radicals can lead to undesirable effects such as browning. Within this work, the diffusion of UV additives and their impact on the degradation behavior of encapsulation material based on ethylene-vinyl acetate copolymer (EVA) is investigated. The fabricated test specimens (glass/EVA/PTFE/glass) were prepared with an artificially created UV additive concentration gradient and weathered under IEC 62788-7-2-A3 conditions. Test points with included UV additives showed no degradation effects, while test points without UV additives showed strong degradation. Surprisingly, the UV additives used could diffuse up to 4 cm within 1500 h weathering. They were able to effectively protect an area of 1.3 cm next to the concentration gradient. Therefore, minor inhomogeneities during the manufacturing process can probably be compensated by intrinsic UV additive diffusion. However, this simultaneously represents a high risk of reaction with residual crosslinking peroxides leading to the UV stabilizer depletion and eventually to browning.