Hydrofluoric acid is part of the acidic etch solution used to remove saw damage from and add texture to multicrystalline silicon wafers. Monocrstyalline wafers are treated with alkaline solutions of e.g. potassium hydroxide.

https://pv-manufacturing.org/acid-texturing/

https://pv-manufacturing.org/alkaline-texturing/

Since the industry is rapidly shifting to monocrystalline silicon, for reasons of cell efficiency, acidic etching too will be much less common in 2025 than it was in 2015.

Of course the use of HF is not a knock against solar. Nuclear fuel production also uses HF as well as elemental fluorine. Petroleum alkylation units use HF too. In all these cases the HF is part of the production process but is not present in the final product.