Why are Pb-Halide Perovskites so Resilient and How is Their Doping Affected by This?

For progress in science, distinguishing ideas or suggestions from robust experimental/theoretical results, is critical.<i> </i>Such is the case for the widespread use of “defect tolerance” (DT) of Halide Perovskites (HaPs), which became a “fact” without direct experimental evidence, similar to their <i>bulk </i>doping. Both are critical to the exceptional optoelectronic properties of HaPs in solar cells, LEDs and detectors, and…. they are related. DT in semiconductors means that structural defects do not lead to (opto)electronically active effects. We found the first direct experimental evidence for DT in Pb-HaPs and will argue that the dynamic Coulombic screening in these intrinsically “soft” and polarizable materials underlies both (our earlier discovered) Self-Healing and their DT<i>.</i> <i>The low doping of HaPs results directly from their SH+DT.</i> In fact, doping them as done for Si or GaAs, does not work. Instead, the default explanation for nearly all reported Pb-HaP doping is via their surfaces and interfaces. While not unique (it works for other semiconductors), here the process dominates, because of their low bulk and relatively low surface defect densities. This understanding explains why, in the end, HaPs present a turbo-version of Kroemer’s “the interface is the device”.<br/><br/>work with A. Kahn (Princeton Univ.), G. Hodes (Weizmann Inst.), and Y Rakita (Ben Gurion Univ.).+++