Determination of the structural phase and octahedral rotation angle in halide perovskites

Abstract

A key to the unique combination of electronic and optical properties in halide perovskite materials lies in their rich structural complexity. However, their radiation sensitive nature limits nanoscale structural characterization requiring dose efficient microscopic techniques in order to determine their structures precisely. In this work, we determine the space-group and directly image the Br halide sites of CsPbBr3, a promising material for optoelectronic applications. Based on the symmetry of high-order Laue zone reflections of convergent-beam electron diffraction, we identify the tetragonal (I4/mcm) structural phase of CsPbBr3 at cryogenic temperature. Electron ptychography provides a highly sensitive phase contrast measurement of the halide positions under low electron-dose conditions, enabling imaging of the elongated Br sites originating from the out-of-phase octahedral rotation viewed along the [001] direction of I4/mcm persisting at room temperature. The measurement of these features and comparison with simulations yield an octahedral rotation angle of 6.5°(±1.5°). The approach demonstrated here opens up opportunities for understanding the atomic scale structural phenomena applying advanced characterization tools on a wide range of radiation sensitive halide-based all-inorganic and hybrid organic-inorganic perovskites.

Single-Source Thermal Evaporation Growth and the Tuning Surface Passivation Layer Thickness Effect in Enhanced Amplified Spontaneous Emission Properties of CsPb(Br0.5Cl0.5)3 Perovskite Films

“…The XRD pattern shows several diffraction peaks, specifically, peaks at 15.97°, 22.42°, 28.49°, 31.86°, and 39.06°. At room temperature, the CsPb(Br 0.5 Cl 0.5 ) 3 perovskite thin film has an orthorhombic structure in space group Pnma [ 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ]. These theoretical data have appeared in consistency to experimental data.…”

Four-Dimensional Scanning Transmission Electron Microscopy (4D-STEM): From Scanning Nanodiffraction to Ptychography and Beyond

“…Additionally, this paper also used simulations to determine that defocused-probe iterative ptychography outperformed both focused-probe iterative ptychography and the WDD reconstruction method by approximately a factor of 2 for signal-to-noise. Various authors have applied ptychography to solve materials science questions, including Yang et al (2015 a , 2017), Wang et al (2017), dos Reis et al (2018), Lozano et al (2018), and Fang et al (2019).…”

Electronic and optical properties of bulk and surface of CsPbBr3 inorganic halide perovskite a first principles DFT 1/2 approach

“…On the other hand, calorimetric investigations on the formation enthalpies of CsPbX perovskites have shown the diminishing order of thermodynamic stability for CsPbCl , CsPbBr , and CsPbI 29 . From various studies it has been reported that CsPbBr undergoes structural phase transitions from orthorhombic to tetragonal and subsequently to cubic at higher temperatures 30 – 36 .…”