We studied the carrier dynamics in planar methyl ammonium lead iodide perovskite films using broadband transient absorption (TA) spectroscopy. We show that the sharp optical absorption onset is due to an exciton transition that is inhomogeneously broadened with binding energy of 9 meV. We fully characterize the TA-spectrum by free-carrier induced bleaching of the exciton transition, quasi-Fermi energy, carrier-temperature and bandgap renormalization constant. The photo-induced carrier temperature is extracted from the TA spectra and monitored as a function of delay time for different excitation wavelengths and photon fluences. We find an efficient hot-phonon bottleneck that slows down cooling of hot carriers by 3-4 orders of magnitude in time above a critical injection carrier density of ~5x10<sup>17</sup> cm<sup>-3</sup>. Compared to molecular beam epitaxially (MBE) grown GaAs the critical density is an order of magnitude lower and the relaxation time is ~3 orders of magnitude longer.

Hot phonon-bottleneck in lead halide perovskite films

251st National Meeting (2016)

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