the side windows in my 5C (a little older than yours) are laminated safety glass like current auto windshields. Not tempered glass. Lexan is an iffy choice for windows since it scratches and hazes really easily. There are versions of Lexan that have some coating that makes them more scratch resistant. Lexan is really easy to work with, I make race car windshields out of it, I use my wood bandsaw and regular drills. Other types of plastic need a lot more care, special saws and drills or they crack like crazy.
Brian