The idea is still a real stretch, but according to Google's paper in Joule [1] they're putting satellites in low Earth orbit and only targeting a service lifetime of 5 years. Over that short time, with the correspondingly modest radiation exposure, you can use inexpensive silicon solar cells like you would use for terrestrial solar farms. The expensive space grade solar cells from e.g. Boeing Spectrolab are more resistant to radiation, and achieve higher conversion efficiencies, but silicon cells are fine for satellites like these.

Starlink satellites already use silicon solar cells, since they too are cost sensitive and don't have long lifespans:

https://starlink.com/public-files/Starlink_Approach_to_Satel...

On the Starlink V2 mini satellite, we predict that approximately 5% of the mass of the entire satellite could survive reentry. The biggest contributor (~90% of the surviving mass) is silicon from the solar cells, which has a high melting point...

[1] https://www.cell.com/joule/fulltext/S2542-4351(26)00362-4