Research progress of anti-reflective coating in photovoltaic cell technology application

A technical challenge for the photovoltaic industry is how to improve the photoelectric conversion efficiency
of solar cells.
However, in addition to the photoelectric conversion efficiency, if the sunlight is reflected by the cell, it means that part of the sunlight will not reach the surface of the solar cell, which is not conducive to energy output
.
Untreated glass surfaces reflect up to 4% of sunlight – this part of the light is lost and cannot be converted into electricity
.

How to reduce unnecessary reflections is an important part of
modern photovoltaic design.
An effective way to achieve this is to use anti-reflective coatings (ARCs) to reduce reflection levels and increase the energy output
of solar modules.

Dr.
Roger Welser, Chief Technology Officer of Magnolia Solar, said: "Anti-reflective coatings can reduce glare, flicker and unwanted reflections caused by smooth surfaces, and can increase the optical power output
of optoelectronic devices such as solar cells and optical sensors.
”

There are many studies on anti-reflective coating (ARC), and the representative research institutions and research trends of ARC technology are as follows:

ARC - University of Florida

Researchers at the University of Florida have studied anti-reflective techniques
based on moth-eye structures.

In recent years, research institutes have developed a number of innovative anti-reflective coatings
.
One interesting example comes from the University of Florida, an anti-reflective technique
based on motheye structures.
According to Dr.
Peng Jiang, an associate professor in the Department of Chemical Engineering at the University of Florida, the eyes of moths have a "periodic sub-wavelength structure"
composed of a regularly arranged papilla structure.
Moth eyes are very dark, not because there is any pigment in the moth eye, but because of the corneal structure
of their eye.

"Our technology can mimic these structures on a variety of substrates, causing reflection inhibition," Professor Jiang said
.

The technology was developed to overcome the shortcomings
of some of the "traditional" quarter-wavelength silicon nitride or titanium dioxide coated structures coated on the surface of silicon cells in photovoltaic modules.
Professor Jiang said that the motheye structure shows "broadband" anti-reflection
compared to traditional dielectric coatings.

"Motheye structures can be made on the substrate body, and we use bottom-up colloidal self-assembly to make these structures
.
Such process developments can be mass-produced
.
Our technology is also applicable to a variety of substrates, including monocrystalline and polycrystalline silicon, gallium arsenide and glass," Jiang Peng said
.

Sharp announced last year that it had developed displays based on the motheye principle, but Jiang Peng said that these structural technologies have not yet been used in
photovoltaic cells.
At present, batteries made using similar structures have come out and are showing higher efficiency - Jiang Peng is actively exploring opportunities
to further commercialize the technology.

ARC - DSM Innovation Center

"The anti-reflective coating reduces unwanted reflections from flat surfaces that cause glare, flicker.
.
.
”

Meanwhile, the Netherlands-based DSM Innovation Center has developed a nanoporous coating technology, commercially known as KhepriCoat
.
The coating was initially used for testing and sale of frame use, and later an optimized version
was developed for solar applications.

Leo Smit, Director of Brand and Communications at DSM's Innovation Center, explains that creating by shang in a very thin coating?? The nanometer porous air gap causes the refractive index to decrease
.

"Essentially, our technique creates a series of nanopores in a solid coating and forms a closed surface and very good adhesion on the glass," Smitt said
.

Following its recent acquisition of Solar Excel, the company has also developed a new light-trapping technology that improves efficiency
by allowing light to get trapped inside a component rather than reflected outside it.

Lighttrapping technology is still being developed – but KhepriCoat coatings are already a commercial product, says Smit: "coated glass 'is being used by numerous solar module producers around the world'.
"
”

ARC - Magnolia Solar Research Center

In the United States, Magnolia Solar, based in Woburn, Massachusetts, and Albany, New York, has also developed anti-reflective coatings
for broadband nanostructures.
It originally grew out of research by the Defense Advanced Research Projects Agency (DARPA) and the New York State Energy Research and Development Authority (NYSERDA
).

Welser explained that by designing the optical properties of the coating material, Magnolia Solar's advanced nanostructured optical coating is able to reduce reflections
over a wide spectral and angular range.
"Our coatings suppress off-angle reflections, thereby minimizing unwanted flicker and glare from PV modules
.
"

The coating can be applied to a variety of surfaces, including rigid glass substrates and flexible plastic sheets, surpassing conventional quarter-wavelength anti-reflective coatings
at all wavelengths and angles of incidence.

Other apps

More generally, anti-reflective coatings are also used in a variety of other applications
.
For example, they can be used in a variety of places
where light reflection needs to be reduced.
For example, lampshades, displays, etc.
, each application has its own requirements, which requires specific product development
.

Jiang Peng also said that in general, anti-reflective coatings and those suitable for glass surfaces can help reduce visual glare
.
He also noted that motheye construction could also be used for light-emitting diodes (LEDs) to improve light extraction
.