Diamondoid solar cell

How does one construct a solar cell material with just carbon or some abundant elements (N,O,P,S,(Fe??),..) too?
Bent graphene can be a tunable semiconductor as was found with nanotubes.
A direct conversion into mechanical energy might be to consider.
[Todo: how much research exists - what is missing?]

Diamond seems to be an excellent material for solar cells. Article: Turning diamond film into solar cells
[Todo: better references needed]

Related

• rectenna (leave to wikipedia) for optical wavelengths with nanotube diodes that are able to switch fast enough non mechanical technology path
• radiation protection
• photonic crystals