I think solar cells get pretty hot. They're not very efficient, and they basically have exactly the smallest albedo they can have, so it's a pretty hot thing to make a roof out of. Hopefully they insulate the backsides of them.
tin works pretty well and it's a pretty hot thing to make a roof out of, having an air gap between your car and the heat source makes a massive difference rather than it being heated directly
A vehicle under direct sun will get hotter than if it's under a roof made of solar panels. Insulating the underside of the panels will reduce their lifespan.
