Structural Disorder in Layered Hybrid Halide Perovskites: Types of Stacking Faults, Influence on Optical Properties and Their Suppression by Crystallization Engineering

Abstract

Layered hybrid halide perovskites (LHHPs) are an emerging type of semiconductor with a set of unique optoelectronic properties. However, the solution processing of high-quality LHHPs films with desired optical properties and phase composition is a challenging task, possibly due to the structural disorder in the LHHP phase. Nevertheless, there is still a lack of experimental evidence and understanding of the nature of the structural disorder in LHHPs and its influence on the optical properties of the material. In the current work, using 2D perovskites (C4H9NH3)2(CH3NH3)n−1PbnI3n+1 (further BA2MAn−1PbnI3n+1) with n = 1–4 as a model system, we demonstrate that deviations in LHHPs optical properties and X-ray diffraction occur due to the presence of continuous defects—Stacking Faults (SFs). Upon analyzing the experimental data and modeled XRD patterns of a possible set of stacking faults (SFs) in the BA2MAPb2I7 phase, we uncover the most plausible type of SFs, featured by the thickness variation within one perovskite slab. We also demonstrate the successful suppression of SFs formation by simple addition of BAI excess into BA2MAn−1PbnI3n+1 solutions.

Quasi-2D Ruddlesden–Popper Lead Halide Perovskites: How Edge Matters

“…The phase purity of the as-prepared nanosheets and thin films of BA 2 MA 2 Pb 3 I 10 was confirmed through conventional characterization techniques, such as X-ray diffraction (XRD) measurements and optical absorption spectroscopy (Figure S1 in the Supporting Information). The diffraction patterns were indexed and found to match well with previous reports. , The excitonic feature at 610 nm could be observed in thin films; the feature exhibited a blue shift in the nanosheets due to its lower dimension.…”

Breaking 1.7V open circuit voltage in large area transparent perovskite solar cells using bulk and interfaces passivation.

“…The (020) re ection, and subsequent multiple [0k0] orientations, was identi ed at 2θ = 4.0°, corresponding to the formation of the [PbI 6 ] 4− octahedral layers. Such orientations and inter-planar spacing typically correspond to a number of 2D layers n = 2 [21][22][23] .These experimental evidences therefore suggest that ISO can form a 3D-2D interface while NEO is expected to be simply adsorbed on the perovskite surface.…”

Optical Properties and Photostability Improvement of CH3NH3PbI3 Treated by Iodide of Long H3N(CH2)10COOH Bifunctional Cation in “2D/3D” and “Monolayer” Passivation Modes

“…The red crystals from FA-containing solution also have a structure of a (100)-oriented layered perovskite with the layer number n = 2, where the [FAPb 2 I 7 ] 2– layers are stacked with AUDA + bilayers in a similar manner (Figure c). The (AUDA) 2 (MA)­Pb 2 I 7 is isostructural to the FA-based counterpart but has a higher degree of organic cation disorder or stacking faults well known for 2D HHPs , which hinder a qualitative refinement of its structure. Two unusual features of layered AUDA-based perovskites are a negligible extent of interdigitation of the interlayer cations as dictated by strong interaction of terminal carboxylic groups and a relatively small angle between the main carbon chain of the cation and the plane of perovskite slabs.…”