That's 90% of the material being recovered from old solar panels, not 90% of new panels being made up of recycled material.

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.