Pyridine-Induced Dimensionality Change in Hybrid Perovskite Nanocrystals

Abstract

Engineering the surface energy through careful manipulation of the surface chemistry is a convenient approach to control quantum confinement and structure dimensionality during nanocrystal growth. Here, we demonstrate that the introduction of pyridine during the synthesis of methylammonium lead bromide (MAPbBr3) perovskite nanocrystals can transform three-dimensional (3D) cubes into two-dimensional (2D) nanostructures. Density functional theory (DFT) calculations show that pyridine preferentially binds to Pb atoms terminating the surface, driving the selective 2D growth of the nanostructures. These 2D nanostructures exhibit strong quantum confinement effects, high photoluminescence quantum yields in the visible spectral range, and efficient charge transfer to molecular acceptors. These qualities indicate the suitability of the synthesized 2D nanostructures for a wide range of optoelectronic applications.

Probing molecule-like isolated octahedra via phase stabilization of zero-dimensional cesium lead halide nanocrystals

“…The basic building block in these material is PbX 6 octahedra (where X is a halogen), whose diverse connectivity can produce structures with various dimensionalities, ranging from three-dimensional (3D) to zero-dimensional (0D) 5–7 . The 3D inorganic perovskites, with general formula APbX 3 (A = Cs, Rb, and X = Cl, Br, or I), consist of an extended network of corner-sharing PbX 6 octahedra with cavities occupied by A ions 8,9 .…”

Recent advances and prospects toward blue perovskite materials and light‐emitting diodes

“…Although lead halide perovskites have a high defect tolerance compared to conventional semiconductor NCs (ie, CdSe, InP), the presence of typical defects such as undesirable cation or anion vacancies tends to cause trapped energy levels that fall within the CB (conduction band) and VB (valence band). This leads to a significant loss in carrier radiative recombination . These defects may deteriorate the short‐range order of the lattice and act as trapping centers of photo‐generated carriers, such as vacancies or distorted [PbX 6 ] octahedra on the surface and inside the perovskite.…”

“…The presence of chlorine causes a large number of defects in perovskite QDs compared to pure bromine analogues . The cation or anion vacancies tend to trap energy between the CB and VB, resulting in a nonradiative recombination process . The ligand passivation strategy introduced into CsPbBr 3 QDs was reported by Li et al in order to increase PL efficiency.…”

“…This leads to a significant loss in carrier radiative recombination. 93,94 These defects may deteriorate the short-range order of the lattice and act as trapping centers of photo-generated carriers, such as vacancies or distorted [PbX 6 ] octahedra on the surface and inside the 46 Copyright 2017 American Chemical Society. C, Steady-state optical absorption and PL spectra for the CsPbCl 3 NCs dispersed in hexane before and after YCl 3 surface passivation.…”

Metal Halide Perovskites: From Crystal Formations to Light‐Emitting‐Diode Applications

“…The size, shape, and emission wavelength can be controlled by tuning the reaction temperature and reaction time. 2D nanoplates and 1D nanowires can be formed by ligand engineering, reaction‐temperature engineering, purification, ultrasonication, A‐site‐cation engineering, or by using additives . Furthermore, the synthesized MHP NCs can be also post‐transformed from 3 nm thick CsPbBr 3 nanosheets to Pb nanoparticle (NP)–CsPbBr 3 nanocomposites by electron beams, from 2D CsPbBr 3 nanoplatelets to larger structures such as nanobelts or square‐shaped nanodisks by photoirradiation, or from cubic phase to orthorhombic phase in FAPbBr 3 crystals by pressure …”