> The silicon is downcycled to steel alloying or similar industrial use.

There is no need to do that. Used solar cells are purer silicon than what comes out of carbothermal reduction of quartz sand to 98.5% pure silicon metal. So you can throw them into the process at that point. The reduction to metal is very energy intensive, so recycling will reduce the energy to make new panels.

They probably are not doing it yet because the volume is so low. Silicon steel is used in transformers and motors, and is even less picky about impurities. So they would just throw the old cells in.