Source: Worked with ppl making the stuff. Acids, dust from cutting, energy, materials. Yes, carbon emissions are less than coal powerplant, but making solar panels produce its share of toxic, non degradable stuff you wouldnt get from powerplant. At least not with regulations we have here in EU. Idk how other parts of the world handle dust and such.
It is thanks to its reputation as “clean” power source that enviroment impact of making solar panel and its ingredient is overlooked.