Abstract: This invention relates to a method for producing films of semiconducting material based on the organic-inorganic metal-halide compounds with perovskite-like structure, which can be used as a light-absorbing layer in solar cells, including thin-film, flexible and tandem solar cells, as well as can be applied for optoelectronic devices, in particular, light emitting diodes. The method is comprising the following steps: (a) applying a layer of a precursor, (b) applying a layer of composite reagent, and (c) treatment of the applied layers by the reagent X2 wherein the composite reagent applied in the step b) contains a mixture of AX and X2 reagents, and the film obtained after the step b) contains the seeds of the phase with a perovskite-like structure; the reagent AX is a salt comprising cation A+ and anion X?, and the anion X? is a singly charged anion; the reagent X2 is a molecular halogen.