The mechanism of slow hot-hole cooling in lead-iodide perovskite: First-principles calculation on carrier lifetime from electron-phonon interaction

We report on an analysis of hot-carrier lifetimes from electron-phonon interaction in lead iodide perovskites using first-principles calculations. Our calculations show that the holes in CsPbI<inf>3</inf> have very long lifetimes in the valence band region situated 0.6 eV below the top of the valence band. On the other hand, no long lifetime is predicted in PbI<inf>3</inf>^-. These different results reflect the different electronic density of states (DOSs) in the valence bands, that is, a small DOS for the former structure while a sharp DOS peak for the latter structure. We propose a reduction of the relaxation paths in the small valence DOS as being the origin of the slow hot-hole cooling. Analyzing the generalized Eliashberg functions, we predict that different perovskite A-site cations do not have an impact on the carrier decay mechanism. The similarity between the DOS structures of CsPbI<inf>3</inf> and CH<inf>3</inf>NH<inf>3</inf>PbI<inf>3</inf> enables us to extend the description of the decay mechanism of fully inorganic CsPbI<inf>3</inf> to its organic-inorganic counterpart, CH<inf>3</inf>NH<inf>3</inf>PbI<inf>3</inf>.