Solar cells are a great technology that, these days, can be put into just about any design. While mono-silicon and poly-silicon cells still require rigid substrates, Perovskite cells, dye-sensitized cells and amorphous silicon cells can all be used in a wider variety of applications.

Solaires makes these, they don't have flexible cells available though, which makes integrating these much trickier without making custom cells from their "solar ink."

Right now they're only suitable for indoor use.