When it comes to the implementation of photovoltaic (PV) systems, the performance and durability of solar cells are two of the most important variables. Due to the fact that it possesses outstanding transparency, flexibility, and adhesive qualities, ethylene-vinyl acetate (EVA) is currently being utilized extensively as an encapsulant material in solar modules. On the other hand, problems associated with aging and acidification can have a substantial impact on the efficiency and durability of EVA, which in turn can have an effect on the comprehensive performance of solar cells. This article explores the mechanisms that are responsible for these issues, the effects that they have on the performance of solar cells, and the various solutions that may be implemented to address these concerns.

Comprehending the Concept of EVA Photovoltaic Film

EVA is a copolymer that is generally utilized in solar modules for the purpose of encapsulating and protecting solar cells from environmental elements such as moisture, ultraviolet radiation, and mechanical stress. EVA is manufactured from ethylene and vinyl acetate for its composition. In addition to preserving the optical clarity that is essential for effective light absorption, it guarantees that the cells will be provided with electrical insulation. However, much like any other polymer, EVA is susceptible to deterioration over time, particularly when it is subjected to extreme weather conditions.

EVA’s Process of Getting Older

The most common causes of aging in EVA encapsulants are prolonged exposure to ultraviolet radiation, heat, and oxygen from the environment. This exposure causes a number of chemical changes inside the substance, including the following:

As a result of photodegradation, the chemical bonds in EVA can be broken by ultraviolet radiation, which then results in the creation of free radicals. These radicals are capable of undergoing further reactions with oxygen, which can lead to the production of a variety of degradation products, including acetic acid and volatile organic compounds (VOCs).

The breakdown of EVA’s polymer chains is accelerated by higher temperatures, which results in discoloration and a loss of mechanical capabilities. This phenomenon is referred to as environmental degradation. This causes the material to become brittle, which in turn reduces its capacity to adequately shield the solar cells.

In the process of oxidative degradation, oxygen penetration can result in oxidative reactions within the EVA, which can then lead to the formation of peroxide molecules and speed up the degradation process.

EVA’s acidification process

The term “acidification” refers to the process by which acidic chemicals, more specifically acetic acid, are formed within the EVA encapsulant. The mechanisms of photodegradation and heat degradation are directly responsible for the occurrence of this condition. A number of unfavorable impacts on the solar module can be caused by the presence of acetic acid within the encapsulant, including the following:

Interconnects and Metal Contacts Corrosion：Acetic acid has the ability to corrode the metal contacts and interconnects that are contained within the solar module. This can result in an increase in electrical resistance and the possibility of electrical failures.

Degradation of Adhesive Properties : The creation of acidic compounds can cause the adhesive properties of EVA to become weaker, which can result in delamination between the encapsulant and the solar cells or the protective glass layer. Because of this delamination, moisture may be able to penetrate, which may further exacerbate the degradation.

Impact on Electrical Performance: The accumulation of acidic chemicals can result in the formation of localized hot spots within the module, which can eventually lead to a reduction in power output and efficiency.

Implications for the Performance of Solar Cells

There is a major risk that the performance and lifetime of solar cells will be significantly hindered by the aging and acidity of EVA encapsulants. The following are the primary effects:

EVA can get discolored and lose its transparency as it deteriorates, which can result in a reduction in its optical clarity. Because of this drop in optical clarity, the amount of sunlight that reaches the solar cells is reduced, which in turn results in a decrease in the power output of the solar cells.

Rising Series Resistance: The corrosion of metal contacts and interconnects that occurs as a result of acidic substances can lead to an increase in the series resistance of the solar module, which in turn results in increased power losses and a decrease in efficiency.

Potential Induced Degradation (PID): EVA degradation compounds have the potential to increase PID, which is a process in which high voltage potentials between the solar cells and the grounded frame create leakage currents, which in turn reduces the performance of the module.

Mechanical Failure: The brittleness and loss of mechanical integrity that occurs in old EVA can result in the physical damage and failure of the solar cells, which in turn compromises the structural stability of the complete module.

Infiltration of Moisture: Delamination, which occurs when the adhesive characteristics of a module are reduced, allows moisture to permeate the module, which in turn causes more corrosion and degradation of the solar cells and interconnects.

Addressing the Problems of Aging and Acidification in EVA

When it comes to EVA encapsulants, the issues that are faced by aging and acidification have led to the development of numerous solutions and developments, including the following:

UV Stabilizers and Antioxidants: The use of UV stabilizers and antioxidants into the formulation of EVA has the potential to greatly slow down the degradation process. This is accomplished by neutralizing free radicals and protecting the polymer chains from breaking down.

Agents of Cross-Linking: The process of cross-linking leads to the formation of a more robust polymer network, which in turn increases the thermal and mechanical stability of EVA. The material’s susceptibility to thermal degradation is decreased as a result of this augmentation, and its resistance to environmental stress is simultaneously improved.

Barrier Films: The use of barrier films on top of the EVA encapsulant can offer further protection against the entrance of oxygen and moisture, hence significantly increasing the lifespan of the solar module.

Anti-Acid Additives: These additives neutralize acidic chemicals when they are generated during the degradation process. As a result, they prevent the corrosive effects of acetic acid on the metal contacts and interconnects.

The use of co-extruded multilayer films or other encapsulant materials such as polyolefin elastomers (POE) can provide improved resistance to ultraviolet (UV) and thermal degradation while keeping outstanding adhesive qualities. This is one of the advanced encapsulation techniques.

Perspectives on the Future and New Developments

In the realm of photovoltaic encapsulants, research and development are now being conducted with the intention of further improving the quality of performance and durability of solar modules. Nano-additives, which offer greater UV and thermal stability, and self-healing encapsulant materials, which are able to fix tiny defects on their own, are examples of innovations that hold a great deal of promise for the future of solar energy.

Zusammenfassend

COACE is dedicated to the research, development, production, and servicing of Additive für Photovoltaik-Verpackungsfolien, with an R&D team lead by numerous senior engineers and PhDs. The majority of consumers use COACES photovoltaic packaging film additives due to their high transparency, low crystal point, high grafting rate, good fluidity, and high resistivity.

The aging and acidity of EVA photovoltaic film greatly reduce solar cell performance and durability, posing significant challenges. The solar industry can lessen these consequences and enhance the reliability and efficiency of solar modules by better understanding the mechanisms that cause these degradation processes, as well as employing better materials and techniques. To meet the ever-increasing need for sustainable and long-lasting solar energy solutions, constant innovation in encapsulant technology will be critical.To that aim, COACE will continue to work hard to create better products that benefit both photovoltaic films and the overall industry!