I am not an electrical engineer, a chemist or anything like that, so I can't really explain how they are doing. Actually, most of the information I have is proprietary information for now. The only thing I can say is that this company (not an American company) developed a system that is different from the PV. It's based on a chemical reaction that I couldn't explain even if I knew it and that's what makes this paint/film so efficient.
The advantages are obviously the price (no need of expertise besides being able to paint a wall) and the fact that it generates a lot of energy without the need of heavy panels.
The disadvantage is that the lifetime is a bit shorter than the panels. You would need to repaint your walls every ten years or so.
I'm trying to contact my friend in the company to see if I can deliver any more info on that. I'll post here whenever they start releasing the info.
Anyway, all this just to say that solar is only in its infancy as a power source, while ICE, well, is not.