Engineers at the Massachusetts Institute of Technology say their polymer coating can be used to protect photovoltaic modules, due to its impermeability to gases. The team has shown that a 60 nanometer thick film can extend the life of a perovskite crystal by several weeks.
A team at the Massachusetts Institute of Technology (MIT) has developed a lightweight polymer film that can be used as a protective coating on solar panels because it is virtually impermeable to gas molecules.
Under laboratory test conditions, the nanometer-thick polymer was found to completely repel nitrogen and other gases. This differs from traditional polymers, which allow gases to pass through because their molecules are loosely bonded together, leaving small openings for gases to pass through.
The lab’s new material, known as 2DPA-1, is a two-dimensional polymer that self-assembles into molecular sheets using hydrogen bonds. It contains a building block called melamine, which contains a ring of carbon and nitrogen atoms, which can expand in two dimensions to form nanometer-sized disks.
2DPA-1 differs from previous polymers in that the disks are stacked on top of each other and held together by hydrogen bonds between the layers, making the structure strong and stable. MIT claims the polymer is stronger than steel, but has only one-sixth the density.
The MIT research exposed 2DPA-1 to helium, argon, oxygen, methane and sulfur hexafluoride and found that its permeability to these gases was at least 1/10,000 that of any other existing polymer, making it almost as impermeable as graphene.
Scientists have been working to develop a graphene coating as a method to protect solar cells from corrosion, but scaling up a graphene film has proven difficult because the film cannot be painted onto surfaces. Because MIT’s 2DPA-1 polymer sticks easily due to the strong hydrogen bonds between the layered disks, it could be a valuable alternative.
In the research paper “A molecularly impermeable polymer made from two-dimensional polyaramids”, available in naturethe research team shows that a 60 nanometer thick film could extend the life of a perovskite crystal by weeks, before adding a thicker coating could provide longer protection.
“By using an impermeable coating like this, you can protect infrastructure like bridges, buildings, railroads – basically anything outside exposed to the elements,” said Michael Strano, MIT’s Carbon P. Dubbs Professor of Chemical Engineering.
George Schatz, a professor of chemistry and chemical and biological engineering at Northwestern University, who was not involved in the study, called the results “remarkable.”
“Normally, polymers are fairly permeable to gases, but the polyaramids reported in this paper are orders of magnitude less permeable to most gases under conditions of industrial relevance,” Schatz explains.
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