High-Pressure-Induced Comminution and Recrystallization of CH3NH3PbBr3 Nanocrystals as Large Thin Nanoplates

Abstract

High pressure (HP) can drive the direct sintering of nanoparticle assemblies for Ag/Au, CdSe/PbS nanocrystals (NCs). Instead of direct sintering for the conventional nanocrystals, this study experimentally observes for the first time high-pressure-induced comminution and recrystallization of organic–inorganic hybrid perovskite nanocrystals into highly luminescent nanoplates with a shorter carrier lifetime. Such novel pressure response is attributed to the unique structural nature of hybrid perovskites under high pressure: during the drastic cubic–orthorhombic structural transformation at ≈2 GPa, (301) the crystal plane fully occupied by organic molecules possesses a higher surface energy, triggering the comminution of nanocrystals into nanoslices along such crystal plane. Beyond bulk perovskites, in which pressure-induced modifications on crystal structures and functional properties will disappear after pressure release, the pressure-formed variants, i.e., large (≈100 nm) and thin (<10 nm) perovskite nanoplates, are retained and these exhibit simultaneous photoluminescence emission enhancing (a 15-fold enhancement in the photoluminescence) and carrier lifetime shortening (from ≈18.3 ± 0.8 to ≈7.6 ± 0.5 ns) after releasing of pressure from 11 GPa. This pressure-induced comminution of hybrid perovskite NCs and a subsequent amorphization–recrystallization treatment offer the possibilities of engineering the advanced hybrid perovskites with specific properties.

High pressure (up to tens of gigapascals), as a clean and powerful tool, can effectively alter crystal structures. Here, it is experimentally investigated for the first time whether pressure can regulate the comminution and recrystallization of MAPbBr₃ nanocrystals. The initial nanocrystals slide into nanoslices during phase transformation to the orthorhombic polymorph, followed by recrystallization into nanoplates upon amorphization.

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