In Situ Transmission Electron Microscopy Study of Electron Beam-Induced Transformations in Colloidal Cesium Lead Halide Perovskite Nanocrystals

Abstract

An increasing number of studies have recently reported the rapid degradation of hybrid and all-inorganic lead halide perovskite nanocrystals under electron beam irradiation in the transmission electron microscope, with the formation of nanometer size, high contrast particles. The nature of these nanoparticles and the involved transformations in the perovskite nanocrystals are still a matter of debate. Herein, we have studied the effects of high energy (80/200 keV) electron irradiation on colloidal cesium lead bromide (CsPbBr3) nanocrystals with different shapes and sizes, especially 3 nm thick nanosheets, a morphology that facilitated the analysis of the various ongoing processes. Our results show that the CsPbBr3 nanocrystals undergo a radiolysis process, with electron stimulated desorption of a fraction of bromine atoms and the reduction of a fraction of Pb2+ ions to Pb0. Subsequently Pb0 atoms diffuse and aggregate, giving rise to the high contrast particles, as previously reported by various groups. The diffusion is facilitated by both high temperature and electron beam irradiation. The early stage Pb nanoparticles are epitaxially bound to the parent CsPbBr3 lattice, and evolve into nonepitaxially bound Pb crystals upon further irradiation, leading to local amorphization and consequent dismantling of the CsPbBr3 lattice. The comparison among CsPbBr3 nanocrystals with various shapes and sizes evidences that the damage is particularly pronounced at the corners and edges of the surface, due to a lower diffusion barrier for Pb0 on the surface than inside the crystal and the presence of a larger fraction of under-coordinated atoms.

Advances in Quantum‐Confined Perovskite Nanocrystals for Optoelectronics

“…However, as postulated by us and other groups and now confirmed by Manna and co-workers, the newly formed spherical particles turn out to be metallic lead (Pb), as determined by EDS and careful HRTEM measurements. [8,42] These spherical particles were previously often claimed to have been perovskite quantum dots, although the size of these stood in conflict with the observed optical properties of the nanoparticles, which tended to be bulklike. [18,24] As such, it would make sense to reinvestigate some of the synthetic procedures and reassess the obtained materials.…”

“…Additionally, a lowering of the substrate temperature reduces the migration of ions and atoms, retarding the degradation mechanisms. [42] Nevertheless, conventional TEM cannot provide nanoplatelet thickness, which is vital information needed to understand the quantum confinement effects. One method with which to obtain the thickness of single nanoplatelets lying flat on substrates is atomic force microscopy (AFM).…”

Strategy to overcome recombination limited photocurrent generation in CsPbX3 nanocrystal arrays

“…13,14 As a new class of colloidal nanomaterials, lead halide-based perovskite nanocrystals (PNCs) raise strong interest because of their unique properties, yet reveal some new challenges. In particular, these materials present some stability issues: PNCs degrade under an electron beam 15 and undergo structural phase changes or ligand-induced stoichiometry change. 16 As a result, PNCs need to be handled with great care and the conventional method to build conductive nanocrystal-based films need to be revised.…”

Dynamic Surface Reconstruction of 2D Ruddlesden-Popper Halide Perovskite under e-Beam Irradiation

“…1. While the electron beam irradiation effect on the 3D halide perovskite materials have been investigated [5][6][7][8][9], studies on 2D halide perovskites are lacking.Herein we present dynamic surface modification on a BA2MA2Pb3I10 (n=3) 2D perovskite with BA (butyl-ammonium, CH3(CH2)3NH3+) working as QW barrier molecules induced by electron beam in transmission electron microscope. We observed various surface dynamics in atomic level under electron irradiation such as lateral growth in c planes of polytypic PbI2 with 3R, 4H and 2H structures at the edge surface of the 2D perovskite accompanied with simultaneous annihilation of surface plane as can be seen in Fig.…”

“…1. While the electron beam irradiation effect on the 3D halide perovskite materials have been investigated [5][6][7][8][9], studies on 2D halide perovskites are lacking.…”