Photo-carrier induced composition separation in mixed-halide CsPb(I (x) Br1-x )(3) perovskite semiconductors; first-principles calculation

The stability of mixed-halide perovskite CsPb(I x Br1-x )(3) against the composition separation is studied by the first-principles calculations in the presence of photo-generated carriers. It is shown that, in the case without carriers, the mixed phase is stable around room temperature owing to the mixing-entropy effect of halide atoms. When such a mixed phase is irradiated under the light and carriers are generated, on the other hand, the composition-separated phase becomes stable. We showed that the confinement of hole carriers in I-rich regions lowers the system energy and promotes composition separation.