Part of the reason that solar cells aren't on top of every roof everywhere harvesting energy is that they're expensive, and part of the reason that solar cells are expensive is because they're made with exotic elements like indium. How about, let's instead make them with one of the top five most common elements in the entire Universe: say hello to the all-carbon solar cell.
Carbon can be as black as coal or as clear as diamond, and by getting creative, you can harness its strength on a much smaller scale with round carbon buckyballs and long and skinny carbon nanotubes. By getting even more creative, researchers at Stanford have managed to transform different sorts of carbon into all of the pieces you need to create a fully functional solar cell.
A solar cell consists of a bottom electrode, a top electrode, and something in the middle that a sucks up photons and turns them into electrons. In this new solar cell, the top and bottom electrodes are both made of graphene, each of which is just one single carbon atom thick. Meanwhile, the delicious gooey heart of the cell is made of a new material comprised of buckyballs and carbon nanotubes. It sounds complex, but it's not: these cells can be made from films out of solution, a very cheap and easy way to go compared to traditional solar cells, and the resulting structure is flexible and extremely durable.
And now, what you've all be waiting for: the downside! At the moment, these carbon cells are less than 1% efficient, which (in scientific terms) totally sucks. They mostly function in the near-infrared, but the researchers say that they're already working with other carbon structures that should be better at chowing down on visible light as well. And even if the cells top out at, say 5% or something, the comparatively low efficiency could just be made up for in volume: cheap and easy to produce volume. As the researchers speculate, "perhaps in the future we can look at alternative markets where flexible carbon solar cells are coated on the surface of buildings, on windows or on cars to generate electricity."