Time-resolved photoemission spectroscopy of electronic cooling and localization in CH$_3$ NH$_3$ PbI$_3$ crystals

We measure the surface of CH$_3$ NH$_3$ PbI$_3$ single crystals by making use of two photon photoemission spectroscopy. Our method monitors the electronic distribution of photoexcited electrons, explicitly discriminating the initial thermalization from slower dynamical processes. The reported results disclose the fast dissipation channels of hot carriers (0.25 ps), set a upper bound to the surface induced recombination velocity (