Every now and then, customers ask the same question.
"If AR coating improves light transmission, why don't we put AR coating on both sides of the glass?"
At first, the idea sounds completely reasonable.
More coating should mean better performance.
But after working with solar glass for a while, you realize the industry doesn't always work that way.
The front side of the glass and the back side of the glass are actually in very different situations.
The outer surface faces the air. This is where part of the sunlight gets reflected before it even enters the module. The AR coating helps reduce that reflection and allows a little more light to pass through.
That's why the coating on the air side matters.
The other side is different.
Once the light passes through the glass, it reaches EVA or POE. The optical difference between these materials and the glass is much smaller than between glass and air. There simply isn't as much reflection happening there.
So even if another AR layer is added, the improvement is usually much smaller than people imagine.
A few years ago, some people in the industry discussed double-side AR coating quite a lot.
The question always came back to the same point:
Is the extra gain worth the extra process?
For many module manufacturers, the answer was no.
Another reason is practical.
Solar glass goes through a lot before becoming a finished module. Washing, tempering, packaging, transportation, unloading, lamination. Every additional surface treatment means another thing to protect and control.
Factories generally prefer solutions that bring clear benefits without making production unnecessarily complicated.
This is probably why 1AR gradually became the standard choice.
It gives a noticeable improvement in transmittance, the process is mature, and production remains relatively simple.
In the solar industry, not every decision is about chasing the highest possible number.
Sometimes it is about finding a balance that works every day, on every production line, and across millions of modules.
That is where one-side AR coating seems to have found its place.
Nowadays, when people mention AR solar glass, most of them are talking about 1AR glass without even saying it.
It has simply become the version that the industry got used to.
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