Nope. You have to determine the cause of the mold and remedy the situation.

Need more information and photos. Mold is never good, but you’re not going to get the advice you’d like unless you post something more specific.

Thick wallpaper?

Wallpaper would just make it mold faster, and it would eventually cover whole wall, and come through the wallpaper too. Defintely not a good idea. Where there is mold, there is also water, or moisture of some kind. You need to find out where the moisture or the water is coming from, and repair that, and then treat the mold. If it is too bad and is inside the mold, that you need to take the wall down to bare studs, and clean it all off, and put in new insulation, and then new sheetrock. Its not a simple thing to deal with mold, and its also a huge danger to your health, if you dont eliminate it.

I've had mold before too--no fun. To clean it:

Spray down the affected area with hydrogen peroxide, let it sit 5 minutes, wipe it with wet rags, repeat the process. You'll have to replace any insulation, but I've been able to save particle board.