Edge-lit LED panel best materials?
What are the best materials to use for this?


These panels are built in the same way as LCD monitors with LED backlight. Well, monitors have a LCD in front of the backlight panel, but you get the idea. Here's a monitor teardown.

The important part is a thick transparent acrylic plate which acts as a light guide via total internal reflection. It is lit through its edges. And... there is a pattern etched on it which breaks the total internal reflection in order to allow the light to get out through the front side. Without this, the light would only get out of the plate through the edges, and that would be useless.

The acrylic plate is the center of a sandwich, with a white reflector on the back, and one or more sheets of diffuser material in front. A LCD monitor will also have polarizers and, of course, a LCD.

All this is not DIY friendly, but you can get the whole kit for free if you find a busted LCD TV or LCD monitor. Thus... try dumpster diving. Get rid of the LCD and polarizer, and keep only the backlight plate and reflector/diffuser films.