This is false. It is easier and safer to store the waste from modern nuclear power plants than waste from production and used solar panels (which are conveniently outsourced to China now due to poor env regulations there)
Basically, what i've heard before (i only skimmed the source), all solar panel are toxic, because the production create use a lot of chemical and create byproducts. We ignore this, it mostly hit poor areas in China and Africa, and this pollution will disapear in less than a century. The end-of-life is OK for old-style PV. Most "new" type of solar panels however, especially those you put on your own roof, are extremely toxic at their end-of-life, and what's worse is that their toxicity are not due to a chemical compound but to elements. What's even worse is that those elements are heavy metals, so bury even one of those PV panels in the ground and it become cancer-land a few year after.