A solar cell is kinda futile, but exposing the wafer to sunlight produces a voltage, this then could be used as an optoisolator or if you're desperate a very very tiny solar panel.
I started looking because I remembered the story at Bell Labs, they had a chunk of silicon and some junctions had impurities in and by co-incidence he had a desk fan on his desk going, and when he used his oscilloscope he was detecting wave patterns, fluctuations after a bit of further investigation he worked out the fan blades were blocking light, letting light through as the blades spun....
So I wondered if anyone tried to convert a transistor to a phototransistor, not found much except for what I just posted.
50 or so years ago the metal capped OC71 transistor used to work well as a photo-transistor if you removed the black outer coating.
In effect it then became the much more expensive OCP71. At that time the glass encapsulation was filled with what looked like a clear silicon grease.
It didn't take long for the manufacturer to twig onto this trick and started filling the OC71 bodies with a translucent filler which obscured the junction, so ensuring sales of their OCP71