Record Setting Solar Cell
These cells were originally developed to power satellites in space and more recently modified for terrestrial applications.
I got a sample today from the wafer lot that set the world record. It is a triple junction compound semiconductor cell with a lattice-matched 1eV material. What this means is that there are three solar cell regions layered on top of each other, each tuned to a region of the visible light spectrum, and in aggregate harvesting more of the spectrum than other materials sets. Depositing each of these different layers in a crystal lattice despite differences in their inter-atomic distance is a big part of the engineering challenge.