From the perspective of reliability in outdoor applications of solar panels, the selection of photovoltaic film

2024 will be an important year for the survival of the fittest in the photovoltaic industry. Intense competition has led to the iteration of battery technology and the speed of industrial application far exceeding ten years ago.
However, no matter how the battery iterates, and whether to choose POE (Polyolefin Elastomer), EVA (Ethylene Acetate Ethylene Copolymer), or EPE for packaging of double glass modules, single glass modules, or flexible modules, this is always an unavoidable and highly discussed topic.
The heat, oxygen, water, ultraviolet radiation, and biological activities in the environment are the main factors causing material failure. In outdoor applications of photovoltaic modules, besides excluding biological activities, the other four environmental factors cannot be ignored. Therefore, when choosing materials, the first consideration should be the impact of these four factors on the materials.
This article compares the effects of EVA and POE under these four environmental factors, providing a new approach and method for material selection.
1. Heat
Both EVA and POE materials can withstand short-term high temperature exposure of about 150 ℃ after crosslinking, but if the temperature continues to increase, EVA will decompose and release a large amount of acetic acid above 200 ℃. The thermal decomposition temperature of POE needs to be at least 300 ℃.
2. Oxygen
EVA and POE are not easily oxidized at room temperature, but due to the presence of a small amount of free acetic acid monomer in EVA, they will be oxidized at high temperatures. However, POE is all chemically stable hydrocarbon bonds, and the temperature at which it reacts with oxygen is much higher than EVA.
3. Water
From a molecular structure perspective, EVA contains ester groups, which are prone to hydrolysis. The carboxyl end groups produced by hydrolysis further promote the occurrence of hydrolysis reactions, leading to rapid aging of the material. The chemical stability of the entire hydrocarbon chain of POE is very high and is not affected by hydrolysis. On the other hand, the water vapor transmittance of EVA film at 38 ℃ and 90% RH is about 25g/m ^ 2-24 hours, while the water vapor transmittance of POE film is 3g/m ^ 2-24 hours. That is to say, the water vapor transmittance of POE is much lower than that of EVA film, which makes POE not only less prone to hydrolysis, but also has a much higher water blocking ability than EVA, thus providing strong protection for other components inside the component.
4. UV rays
Similarly, POE has a full hydrocarbon chain structure, and its chemical bond energy is high. The C-H bond energy is 414 kJ/mol, and the C-C bond energy is 332 kJ/mol. It is not easily broken when exposed to ultraviolet light on the ground, while the C-O bond energy of the ester group in EVA is less than 330 kJ/mol, which makes it more susceptible to UV radiation and breakage.
In summary, in the use of packaging materials, POE is superior to EVA in terms of the four key elements of outdoor application reliability: heat, oxygen, water, and UV performance. In today's increasingly "high efficiency" and "strict requirements" of batteries, POE is still the best choice to ensure long-term stable and continuous "output" of batteries.