Four phenothiazines were electrochemically copolymerized with thionine from their buffered solutions in order to obtain photoactive layer possessing extended UV-Vis absorption range and thus higher ability to generate singlet oxygen under white light illumination. The synthesized copolymer layers were characterized by means of cyclic voltammetry, Raman spectroscopy and UV-Vis spectroscopy. The latter, confirmed that copolymerization occurred and that the immobilized copolymers exhibit wide absorption band covering the UV and Vis regions. The process of photoinduced singlet oxygen generation was tested using well-known O-1(2)-quencher, i.e. 1,3-diphenylisobenzofuran. The results demonstrate that the immobilized photosensitizers under illumination are capable to generate the active oxygen molecule with a high efficiency. The investigated photoactive materials have been in turn applied in the process of oxidation of 1,5-dihydroxynaphthalene. (C) 2019 The Electrochemical Society.