There are three types of technologies that you might find in solar panels or solar cells:
Monocrystalline Solar Panels
As far as efficiency by square footage, mono crystalline panels are the way to go. Monocrystalline cells also do a great job in high temperatures, only loosing about 12-15% of their power.
Monocrystalline panels typically have a rounded square array of cells as you can see the the left here.
Polycrystalline Solar Panels
The power production in polycrystalline cells is reduced 14% to 23%. That is kind of a high hit to the efficiency at almost 25%! That means you’ve got to have an extra panel to each 4 in order to get the peak ratings advertised in direct sunlight. This could partially explain why they are the cheapest solar technologies.
Polycrystalline panels are typically made up of non-rounded square cells.
Amorphous Solar Panels
Amorphous solar panels are the largest panels, or the least efficient per square foot. They are actually about half as efficient as polycrystalline or monocrystalline cells. They’re also the technology that you’re probably the most familiar with, probably the panel you’d find in your calculator.
It’s also a technology that is very durable and flexible, so panels can be used for a calculator or as a roll that’s used while camping.
Although the lifetime of panels or their cells is difficult to test for sure, it’s believed that amorphous cells loose quite a bit of there power after 15 years.
These are the panels that you see a top a lot of homes because they are so cheap at around $5/watt, and the greatest benefit of all is that they don’t become less efficient in elevated temperatures infact in some cases the input increases slightly in high temperatures.