Provided are infrared films comprising a substrate, a layer of an aminium radical cation compound in a crystalline state and an organic polymer selected from the group consisting of a divinyl ether polymer, a fluoropolymer, and a silicone polymer, and, optionally, a water repellent layer overlying the layer of the aminium compound. Such infrared films are stable in their optical properties and useful for security markings, test strips for analysis of fluids, and other optical articles for detection in the infrared. Also provided are methods for making such infrared films.