  Defect tolerance is a critical enabling factor for efficient lead-halide
perovskite materials, but the current understanding is primarily on band-edge
(cold) carriers, with significant debate over whether hot carriers (HCs) can
also exhibit defect tolerance. Here, this important gap in the field is
addressed by investigating how internationally-introduced traps affect HC
relaxation in CsPbX3 nanocrystals (X = Br, I, or mixture). Using femtosecond
interband and intraband spectroscopy, along with energy-dependent
photoluminescence measurements and kinetic modelling, it is found that HCs are
not universally defect tolerant in CsPbX3, but are strongly correlated to the
defect tolerance of cold carriers, requiring shallow traps to be present (as in
CsPbI3). It is found that HCs are directly captured by traps, instead of going
through an intermediate cold carrier, and deeper traps cause faster HC cooling,
reducing the effects of the hot phonon bottleneck and Auger reheating. This
work provides important insights into how defects influence HCs, which will be
important for designing materials for hot carrier solar cells, multiexciton
generation, and optical gain media.
