On the crystal structure thermal evolution of formamidinium lead tribromide, CH(NH₂)₂PbBr₃

Abstract

A structural study from synchrotron X-ray and neutron diffraction of an undeuterated FAPbBr3 specimen allows identification of two phase transitions (Pm3̄m→P4/mbm→Pnma). Further rearrangements in the H bonds to Br imply thermal events observed by calorimetric measurements.

Lattice dynamics and phase transitions in FAPbBr3 single crystals: Temperature‐ and pressure‐dependent Raman spectroscopy

“…The XRD pattern shows narrow and well‐resolved peaks that are indicative of a high degree of crystallographic order and orientation. The diffraction angles matched well with the literature 23 . Figure 1B exhibits the absorption spectrum of the FAPbBr 3 single crystal, together with insets of the photoluminescence (PL) spectrum and the bandgap calculated using the Tauc plot method.…”

“…The diffraction angles matched well with the literature. 23 Figure 1B exhibits the absorption spectrum of the FAPbBr 3 single crystal, together with insets of the photoluminescence (PL) spectrum and the bandgap calculated using the Tauc plot method. The absorption spectrum shows a clear absorption edge near 567 nm without any evidence of excitonic signatures from trap states thus indicating a defect-free lattice.…”

Phase transition model of FA cation ordering in FAPbX3 (X = Br, I) hybrid perovskites

“…20 Despite extensive use of FAPbX 3 (X = Br, I) in solar cell fabrication, a detailed understanding of the structural phase transitions and cation dynamics in these compounds is still under intense investigation. 19,[21][22][23][24][25][26][27][28][29][30] FAPbI 3 typically crystallizes into the photoinactive yellow hexagonal phase (d), which can be converted to a metastable black cubic phase (a) by thermal annealing. 25,[31][32][33] Upon cooling from the cubic phase, FAPbI 3 exhibits a phase transition at 285 K to a tetragonal phase (b), and another phase transition appears below 140 K (g-phase).…”

A-Site Cation Influence on the Structural and Optical Evolution of Ultrathin Lead Halide Perovskite Nanoplatelets

“…In the crystal structure of FAPbBr 3 , the A-site cation can have several different orientations within the unit cell, leading to a variety of different configurations that exhibit different elastic properties and anisotropies. Geometry optimization was performed on the reported crystal structure of single-crystal FAPbBr 3 , , from which unit cell parameters of a = 8.51 Å, b = 12.10 Å, and c = 8.50 Å are obtained.…”