Carrier-Specific Hot Phonon Bottleneck in CHNHPbI Revealed by Femtosecond XUV Absorption.

Femtosecond carrier cooling in the organohalide perovskite semiconductor CHNHPbI is measured using extreme ultraviolet (XUV) and optical transient absorption spectroscopy. XUV absorption between 44 and 58 eV measures transitions from the I 4d core to the valence and conduction bands and gives distinct signals for hole and electron dynamics. The core-to-valence-band signal directly maps the photoexcited hole distribution and provides a quantitative measurement of the hole temperature. The combination of XUV and optical probes reveals that upon excitation at 400 nm, the initial hole distribution is 3.5 times hotter than the electron distribution. At an initial carrier density of 1.4 × 10 cm both carriers are subject to a hot phonon bottleneck, but at 4.2 × 10 cm the holes cool to less than 1000 K within 400 fs. This result places significant constraints on the use of organohalide perovskites in hot-carrier photovoltaics.