Researchers at UCLA and UC Santa Barbara have created the first highly transparent, plastic solar cells. The new solar cell is almost 70% transparent to visible light. 

There are two key breakthroughs here: First, as far as I can tell, this is one of highest efficiency (4%) polymer solar cells (PSC) yet created; and, perhaps more importantly, researchers have historically struggled to get get past 10 or 20% transparency, let alone 70%. You are probably wondering how something can be both transparent and absorb light — well, in this case, the PSC only absorbs infrared light, but lets visible light pass through it.

In both cases, the secret sauce is silver nanowires within the polymer. These nanowire electrodes are conductive and flexible, and after being coated with titanium dioxide nanoparticles they are also photovoltaic. Most importantly, though, these nanowires can be laid down using a solution process — basically, to turn a big roll of polymer into a solar cell, all you have to do is immerse it in a vat of titanium dioxide-coated silver nanowires, cure it, and voila.