system
Given the following post, respond as if you're commenting on Reddit:
human
How much energy is lost from reflection on solar panels, on average?

How much light that could potentially be turned to electricity is reflected by solar panels?
gpt
Some good information here, some bad information.

There two major sources of reflection off a solar cell. The first is off the top surface metals - both the two thick bus bars and the thin fingers that cover the top surface. All incident light off of those is reflected, so the coverage is the amount lost - usually something like 4%.

The second is related to the index mismatch. Any time light passes through an interface with two different index materials there is a reflection. A good example is the reflection you see off of a glass or water surface. Silicon (the most common solar material) has a very high index - around 4 - so the amount of reflection is quite high. This is reduced by an anti-reflective (AR) coating with intermediate index. You can also use thin film interference to improve the AR coating even more. This is why solar cells appear blue - it is the same reason that a thin film of oil on water causes colors to appear. In this case, green light, which there is a lot of, is absorbed very strongly, and blue less so. 

So the question is "How much light that could potentially be turned to electricity is reflected by solar panels?" - how much of this is inherent loss and how much of it is avoidable?

1. Metalization loss can be completely eliminated through various schemes. Some all back contact cells are currently in production (by an american company called Sun Power) which have no metal in the front. Standard cells can be improved by improving either the conductivity of the metal on the front or the aspect ratio - making it more tall than it is wide. Other possible schemes are nano structured metals which will conduct electricity but not reflect light.

2. Most commercial cells use a single layer AR coating of silicon nitride. Significantly less reflection can be obtained with a dual layer AR coating (and this is used for top performing research cells), but this is both more expensive, and less effective once the cell is encapsulated in glass. Something like a 2.5% efficiency gain should be possible here. 

Finally, the texturing also effects the reflection of the surface. This is also a question of economics. Most commercial cells use base etched surfaces, which create random pyramids. However, the record cell used patterned inverted pyramids which provide less reflection, but is a much more expensive process.