Formation of a two-phase structure in CH$_{3}$NH$_{3}$PbI$_{3}$ organometallic perovskite

The effect of annealing of organometallic perovskite CH$_{3}$NH$_{3}$PbI$_{3}$ film on its electrical, photoelectric, and optical properties is studied. It was shown that annealing at $T_a>$ 140$^{\circ}$C leads to the two-phase structure formation consisting of perovskite and lead iodide, the relative content of which depends on the annealing conditions, in particular, on its temperature. The PbI$_2$ formation in the perovskite structure leads to a decrease in the conductivity and photoconductivity of the material. Our studies indicate the possibility of forming planar structures consisting of semiconductor materials with various values of the band gap: 1.6 eV (CH$_{3}$NH$_{3}$PbI$_{3}$) and 2.4 eV (PbI$_2$).