Polymers and compounds including a diphenylmethylene or a 9H-fluorene moiety; and sunscreen compositions including a mixture of a photoactive compound and any one of the foregoing derivatives are disclosed herein. Also disclosed are methods for stabilizing a sunscreen composition by the addition of one or more of the foregoing derivatives, methods of filtering out ultra-violet light from a substrate by the use of one or more such derivatives, and methods for terminating a polymerization reaction by the addition of derivatives of diphenylmethylene and/or 9H-fluorene. Synergistic combinations of the polymer with (1) diesters or polyesters of a naphthalene dicarboxylic acid, or (2) oxybenzone enhance the photostability of sunscreen compositions containing a photodegradable sunscreen active compound, such as avobenzone.