you mean like foam core cardboard?
no. there is no way.
anything you use to adhere it will be between it and the glass, and that will look crappy.
The best ways to make the back of your tank black are to
1. Paint it (I like acrylic paint on the outside)
2. Use a sheet of plastic for aquariums, squeegie it on with a little cooking oil between it and the glass (eh, not so great imo)
3. Signmakers vinyl on the outside. (squeegie it on with soapy warm water. hard to perfect, but can look perfect)
4. Use black acrylic or expanded pvc INSIDE the aquarium with silicone or magnets.