When developing solar cells researchers and engineers have to strike a balance between efficiency, flexibility, and cost. Generally, the more efficient the material the less flexible and more expensive it is. The cheaper and more flexible the material the less efficient it is. These relationships are true for the time being, but researchers are hard at work to change them.
Researchers at the University of Southern California have been working on liquid solar cells and recently made an important discovery. Liquid solar cells are actually solutions of nanocrystals which produce electricity when light shines on them. These crystals can be made very cheaply and be painted onto any transparent material, like glass or plastic. The catch is the nanocrystals normally have organic ligands attached, to prevent them from sticking together in solution. These ligands resist the electric current produced by the crystals though.
To overcome the resistance of the organic ligands, the researchers developed synthetic ligands which still stabilize the solution but do not resist electricity as much. Liquid solar panels are still years away from being commercial products, but this is an important step towards realizing that future.