most efficient solar cells

Updated several times, last time being March 21, 2015, in order to update the efficiency records.

Reposted from Cost of Solar:

One of the most common things people ask when they start to consider going solar or start to plan their life-changing solar expedition is which are the most efficient solar panels. However, first of all, that’s not even the right question for most people, and second of all, the literal answer to that question really isn’t relevant for the average consumer. Let me explain….

First of all, the important matter is not which solar panels are most efficient, but which solar panels are the best value for the money. If you’ve got space for 10 solar panels on your roof and you have an option between solar panels “ABEfficient” that are a bit more efficient but twice the price of solar panels “CDCheap,” chances are, you are going to make a much bigger savings by going with CDCheap. Of course, the important thing would be to see what’s available in your situation and simply run the numbers (or, if you are allergic to math, have a friend who can do math run the numbers for you).

But, anyway, if you really want to know which are the most efficient solar panels (or solar cells) out there, I actually happened to be putting together a list of solar records recently and can give you the rundown. But, as I do so, I’ll drop in a few key notes making the point above a bit clearer. Before looking at solar panels as a whole, let’s have a quick look at the producers of some of the most efficient solar cells (the key component of solar panels) and their efficiency records:

• 46% efficient solar cells by Soitec & Fraunhofer Institute. Notably, these world-leading solar cells from Soitec and Fraunhofer Institute are in the concentrator quadruple-junction solar cell category. Such solar cells are complicated and are not used in residential or commercial applications… because they are bloody expensive. They are used in space applications by the likes of NASA, where a bit of extra space (or, as it may be, less space via extra efficiency) can make a huge difference.
• 44.4% efficient solar cells by Sharp previously held the overall efficiency record. However, they still hold the record for triple-junction (concentrator) solar cells.
• 37.9% efficient solar cells by Sharp. A big step down, these are in the triple-junction, non-concentrator solar cell category. If this is all new to you, it might take you awhile to see the difference in the categories. The difference is that these solar cells don’t use anything to concentrate the light hitting the solar cells, while the 44.4% efficiency cells noted above do use something to concentrate the light (of course, adding to their costs).
• 32.6% solar cells by a Spanish solar research institute (IES) and university (UPM). These are another step down, as they are in the two-junction, concentrator solar cell category. (For an intro on “junctions,” by the way, check out this multi-junction photovoltaic cell article on Wikipedia.) Again, these are still far different solar cells from what are used in commercial or residential installations.
• There are about a dozen or so extra categories that I could run down. Some categories have very high efficiencies but the solar cells are quite expensive, while others are actually on the other end of the spectrum (no pun intended) and are very cheap but have very low efficiency. Of course, some are both inefficient and expensive, but apparently worth researching nonetheless. The key, as I noted earlier, is finding the best balance between cost and efficiency.