That doesn't pass the sniff test. Solar cell production is on a strong upwards curve, if 80% is recycled from other panels then supply would be bounded by old solar stock recovery, which is not the case.
I can't see how 80% of solar panel material, even if we're talking exclusively about the PV cells and not the surrounds, could be from old solar panels, especially not 30 year old solar panels.
That's still great news, but nothing like:
>80% of the material in solar panels is recycled from old solar panels.
Which implies new panels rolling off the production line consisted of 80% recycled material from old panels. That's not possible. If you have 10 old panels coming in to be recycled, and you recover 90% of the materials from them, and you're producing 100 new panels (since production is increasing), at best you're gonna get 9% recycled material into your new panels.
So no matter how you turn it, solar panels are a lot alot more environmentally friendly than convential energy sources.