Radioactive material that gives light, put in solar panels, to see if the solar panel generates more electricity

Radioactive material that gives light, put in solar panels, to see if the solar panel generates more electricity
-Very slightly radioactive

Only:
1 -For in a power plant (using the very slightly radioactive variant)
  -And with enough safety and safety measures
2 extra:
-For space travel etc. Maybe more radioactive materials can be used then