Colloidal Metal‐Halide Perovskite Nanoplatelets: Thickness‐Controlled Synthesis, Properties, and Application in Light‐Emitting Diodes

Abstract

Colloidal metal‐halide perovskite nanocrystals (MHP NCs) are gaining significant attention for a wide range of optoelectronics applications owing to their exciting properties, such as defect tolerance, near‐unity photoluminescence quantum yield, and tunable emission across the entire visible wavelength range. Although the optical properties of MHP NCs are easily tunable through their halide composition, they suffer from light‐induced halide phase segregation that limits their use in devices. However, MHPs can be synthesized in the form of colloidal nanoplatelets (NPls) with monolayer (ML)‐level thickness control, exhibiting strong quantum confinement effects, and thus enabling tunable emission across the entire visible wavelength range by controlling the thickness of bromide or iodide‐based lead‐halide perovskite NPls. In addition, the NPls exhibit narrow emission peaks, have high exciton binding energies, and a higher fraction of radiative recombination compared to their bulk counterparts, making them ideal candidates for applications in light‐emitting diodes (LEDs). This review discusses the state‐of‐the‐art in colloidal MHP NPls: synthetic routes, thickness‐controlled synthesis of both organic–inorganic hybrid and all‐inorganic MHP NPls, their linear and nonlinear optical properties (including charge‐carrier dynamics), and their performance in LEDs. Furthermore, the challenges associated with their thickness‐controlled synthesis, environmental and thermal stability, and their application in making efficient LEDs are discussed.

Recent Progress in Mixed A‐Site Cation Halide Perovskite Thin‐Films and Nanocrystals for Solar Cells and Light‐Emitting Diodes

“…As can be seen from earlier sections, LHPs are one of the leading candidates for the next generation of optoelectronic applications, including light emission. [ 14,200,201 ] Compositional engineering [ 202 ] and dimensional engineering [ 203 ] are widely used to tune the optoelectronic properties of halide perovskites. In this section, we will focus on A‐site compositional engineering, and discuss the effects on LED device performance.…”

Slowing Down for Growth Mechanism and Speeding Up for Performance Optimization Based on Single Ligand Passivated CsPbBr3 Nanoplatelets

“…The layered NPls exhibit anisotropic transport properties, the out‐of‐plane charge mobility is much smaller than the in‐plane mobility. [ 16 ] Considering the relatively large lateral size of NPls, they prefer parallel to electrode which is averse to carrier transfer in emitting layer. [ 17 ] From device engineering, tailoring the orientation of NPls in emitting layer may be an effective approach.…”

Changing Spin and Orbital Ground State Symmetries in Colloidal Nanoplatelets with Magnetic Fields

“…These are heterostructures in which a seed NPL is laterally surrounded by a different material, forming a crown around the core NPL. [14,15] Because the crown has a doubly connected (toroidal) topology, carriers confined within are liable of displaying phenomena related to the Aharonov-Bohm (AB) effect in the presence of external magnetic fields. [2,26] For illustration purposes, we consider the case of CdSe/CdTe core/crown NPLs.…”

“…This magnitude vastly exceeds the range of energetic modifications that can be induced even by high magnetic fields (up to a few meV for 30 T, when relying on Zeeman splitting). [12,13] The advent of colloidal nanoplatelets (NPLs) in metal-chalcogenide and halide perovskite materials [14,15] may be a turning point in this regard. NPLs are slab-like nanocrystals that combine a strongly confined direction (with a thickness of a few atomic monolayers only) and weak lateral confinement in the other two dimensions (from a few nm to tens of nm).…”