The thin films (~100 nm) based on 2-phenyloxybenzoate terbium(III) doped into a polymer matrix have been obtained. The terbium content in the mixture was varied from 0 to 11 wt.%. The films were prepared on K8 glass by spin coating from a chloroform solution. The presence of a weak antireflection effect was established using light transmission spectra of the films on the glass. According to the excitation and luminescence spectra, there is reemission of light from the spectral range of 240–330 nm to the range of 480–640 nm, where a series of narrow luminescence peaks characteristic of the Tb3+ ion is observed. The effect of the films on the efficiency of three-stage solar cells has been studied.