nz8b01227_si_001.pdf (929.22 kB)
Ultrafast Intraband Spectroscopy of Hot-Carrier Cooling in Lead-Halide Perovskites
journal contribution
posted on 2018-08-21, 00:00 authored by Thomas
R. Hopper, Andrei Gorodetsky, Jarvist M. Frost, Christian Müller, Robert Lovrincic, Artem A. BakulinThe
rapid relaxation of above-band-gap “hot” carriers
(HCs) imposes the key efficiency limit in lead-halide perovskite (LHP)
solar cells. Recent studies have indicated that HC cooling in these
systems may be sensitive to materials composition, as well as the
energy and density of excited states. However, the key parameters
underpinning the cooling mechanism are currently under debate. Here
we use a sequence of ultrafast optical pulses (visible pump–infrared
push–infrared probe) to directly compare the intraband cooling
dynamics in five common LHPs: FAPbI3, FAPbBr3, MAPbI3, MAPbBr3, and CsPbBr3.
We observe ∼100–900 fs cooling times, with slower cooling
at higher HC densities. This effect is strongest in the all-inorganic
Cs-based system, compared to the hybrid analogues with organic cations.
These observations, together with band structure calculations, allow
us to quantify the origin of the “hot-phonon bottleneck”
in LHPs and assert the thermodynamic contribution of a symmetry-breaking
organic cation toward rapid HC cooling.