Structural and Thermal Disorder of Solution-Processed CH₃NH₃PbBr₃ Hybrid Perovskite Thin Films

We extracted the electronic disorder energy of the organic-inorganic lead-halide hybrid perovskite CH₃NH₃PbBr₃ from temperature-dependent absorption data. We showed that the disorder at room temperature is ∼30 meV and is due to strong electron-phonon coupling with the longitudinal-optical mode of energy 16 meV. This mode can be attributed to longitudinal-optical phonons of the inorganic PbBr₆ frame; this conclusion highlights the polaronic nature of electronic excitations in CH₃NH₃PbBr₃. We showed that structural disorder is of the same impact as thermal disorder. A temperature-dependence of the exciton binding energy was observed close to the orthorhombic-to-tetragonal phase-transition temperature.