Antireflection coatings on plastics have many practical applications, such as reducing glare on screens on glasses, computers and smartphones in outdoor environments
Now, researchers at Pennsylvania State University have developed an enhanced version of the antireflection coating that can make transparent plastics (such as Plexiglas) almost invisible
Chris Giebink, associate professor of electrical engineering at Pennsylvania State University, said: “This invention was developed when we made more efficient solar panels .
Our method is to use plastic lenses to focus light on small, high-efficiency solar cells.
Minimize its reflection loss .
" They need an anti-reflection coating that can be applied to the entire solar spectrum and multi-angle illumination, as well as an anti- reflection coating that can withstand the test of outdoor weather for a long time .
"We expected to find a ready-made solution, but none of the solutions can meet our performance requirements," he said .
"So, we started to develop our own solutions .
" This is a tricky problem .
Although it is relatively easy to manufacture an anti-reflection coating that can eliminate light reflected in a specific wavelength or direction, there is no anti-reflection coating that meets all standards .
For example, antireflection coatings for spectacles work against the narrow visible spectrum of the spectrum .
However, the width of the solar spectrum is about five times that of the visible spectrum, so this coating is not suitable for concentrating solar cell systems .
When light travels from one medium (such as air) to a second medium (here, plastic), reflection occurs .
If the two refractive indexes (referring to the propagation speed of light in a specific material) are very different, for example, the refractive index of air is 1, and the refractive index of plastic is 1.
5, a lot of light reflection will occur .
Natural coatings such as magnesium fluoride or Teflon (Teflon) have a minimum refractive index of about 1.
By mixing different materials, the refractive index can be gradually changed between 1.
3 and 1.
5, but when the refractive index is gradually changed to 1.
3, the difference between it and the refractive index of air 1 still exists
In a paper recently published online in Nano Letters, Giebink and his research partners introduced a new technology to eliminate the refractive index gap between Teflon and air .
They used sacrificial molecules (sacrificial molecul) to create nano-scale pores in the evaporated Teflon, and then created a Teflon-air film with a graded refractive index, visually "coaxing" the light, allowing the light to "see" the refractive index from A smooth transition from 1 to 1.
5, which basically eliminates all reflections .
"Interestingly, when you use a crucible to heat a polymer like Teflon, the large polymer chains will split into smaller pieces.
These fragments are small enough to volatilize and emit steam flux .
When they fall on the substrate It will re-polymerize to form Teflon when it goes up.
” Giebink said .
When sacrificial molecules are added, Teflon will reshape around these molecules .
After dissolving the sacrificial molecules, there is a nanoporous membrane that can be changed by adding more pores .
"We have been communicating with companies seeking to improve plastic antireflection coatings, and some of these applications are unexpected," he said .
"From eliminating the glare of the camera’s plastic protective dome to eliminating stray reflections in virtual/augmented reality headsets, this kind of antireflection coating can be used .
" Another more unexpected application is in high-altitude drones or drones.
Man is driving an aircraft .
These aircraft have huge wingspans covered with solar cell coatings .
These aircraft, which are mainly used for reconnaissance, rely on sunlight to maintain uninterrupted flight, so the large amount of light they receive is at the glancing angle with the highest reflection .
One of the companies that make these solar cells is studying this AR coating to see if it can increase the amount of light received by drones
Because the technology is compatible with current manufacturing technology, Giebink believes that the coating technology has scalability and broad application potential .
So far, the test samples have withstood two years of climate test in central Pennsylvania, and there is almost no change in performance .
In addition, the anti-reflection film also has an anti-fog function .
"The coating can adhere well to different types of plastics, but it cannot adhere to glass," he said .
"Therefore, it is not suitable for a specific solar roof with a glass protective cover .
But if concentrated photovoltaic cells will make a comeback, one of the key components of this type of battery is the Fresnel plastic lens.
At that time, we The anti-reflection coating of the company can play a role there .