Halide perovskite dynamics at work: Large cations at 2D-on-3D interfaces are mobile.

Kumar, Sujit; Houben, Lothar; Rechav, Katya; Cahen, David · Proc Natl Acad Sci U S A · 2022

basic_science · Level V

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Abstract

SignificanceSurface engineering of halide perovskites (HaPs), semiconductors with amazing optoelectronic properties, is critical to improve the performance and ambient stability of HaP-based solar cells and light emitting diodes (LEDs). Ultrathin layers of two-dimensional (2D) analogs of the three-dimensional (3D) HaPs are particularly attractive for this because of their chemical similarities but higher ambient stability. But do such 2D/3D interfaces actually last, given that ions in HaPs move readily-i.e., what happens at those interfaces on the atomic scale? A special electron microscopy, which as a bonus also reveals the true conditions for nondestructive analysis, shows that the large ions that are a necessary part of the 2D films can move into the 3D HaP, a fascinating illustration of <i>panta rei</i> in HaPs.