All will be heat after X amount of time. Where the X can be a few seconds or decades or centuries.
The more interesting thing would be the light reflected by the panels (albedo factor). This could be lower or higher than the surface these panels are placed on.
Also, the emittance of the panels at thermal wavelengths is important. What you want is a panel that converts wavelengths shorter than the bandgap cutoff at high efficiency, reflects near and mid IR at longer wavelengths, but has high emissivity in the far IR at wavelengths where the atmosphere isn't too opaque.
