The photoelectric characteristics of transparent ZnO films have been investigated. The possibility of controlling the conductivity by the introduction of impurities is presented. The ratio of conductivities of the films doped with donor and acceptor impurities reaches value of 109. It is shown that it is possible to achieve a significant increase in the ratio of photoconductivity to the dark conductivity in the films doped with Li impurities, which provides a significant reduction in the dark conductivity without changing the conductivity type. This phenomenon can be used to develop the solid state photodetectors of UV range.