  The term defect tolerance (DT) is used often to rationalize the exceptional
optoelectronic properties of Halide Perovskites (HaPs) and their devices. Even
though DT lacked direct experimental evidence, it became a "fact" in the field.
DT in semiconductors implies that structural defects do not translate to
electrical and optical effects (e.g., due to charge trapping), associated with
such defects. We present the first direct experimental evidence for DT in
Pb-HaPs by comparing the structural quality of 2-dimensional (2D), 2D-3D, and
3D Pb-iodide HaP crystals with their optoelectronic characteristics using
high-sensitivity methods. Importantly, we get information from the materials'
bulk, because we sample at least a few hundred nanometers, up to several
micrometers, from the sample's surface, which allows for assessing intrinsic
bulk (and not only surface-) properties of HaPs. The results point to DT in 3D,
2D-3D, and 2D Pb-HaPs. Overall, our data provide an experimental basis to
rationalize DT in Pb-HaPs. These experiments and findings can guide the search
for, and design of other materials with DT.
