My bedroom gets the sun 24/7, if the sun is up, it's shining directly into my room.
I have a rather large collection set up in my room that the sun would have destroyed if left untreated. I couldn't stand complete darkness, so I looked into window film that would block out the sun.
I bought the Gila Glare Control Window Film last summer. I could leave my SS twilight in the window in direct sunlight and it won't harm her.
It claims a 97% rejection of all UV Rays. Best Money I ever spent. I've tested leaving ponies in the window (ponies covered in sharpie/ponies who burn) and not an ounce of damage or sharpie removal.