Construct the third type of nanocrystals-"superlattice" through perovskite

【Research Background】

Perovskite crystals are currently receiving wide attention.
They are composed of at least three different ions and are known for their excellent electrical and optical properties.
They have outstanding application potential in solar cells and optoelectronic devices
.

Studies have shown that when perovskite nanocubes are combined with nanospheres of other materials, the various nanostructures obtained can be arranged into a three-dimensional "superlattice" regardless of whether there is a third type of nanocrystal or not.

【Introduction to Achievements】

Recently, Professor Gerd Bacher of the University of Duisburg-Essen, Germany, interpreted the work that nanocrystals with customized shapes and compositions have been shown to form "superlattice" arrays similar to the ionic lattice of perovskite compounds, and also showed that One of the superlattices exhibits a phenomenon called superfluorescence
.

The paper was published in the well-known journal Nature with the title "Nanocrystals form a superfluorescent lattice mimicking the atomic structure of perovskite materials"

[Picture Guide]

Cherniukh et al.
proved through experiments that the co-assembly of cubic and spherical space-stable nanocrystals is experimentally possible, and the cubic shape of perovskite nanocrystals leads to a completely different result compared to the global-shaped system
.

The author obtained binary supercrystals by mixing nanocubes of perovskite CsPbBr ₃ with spherical nanocrystals of iron oxide (Fe ₃ O ₄ ) or NdGdF ₄

Nanocrystals of a perovskite-like superlattice
.

(A) The combination of spherical, cubic and truncated cubic nanocrystals can form an ordered arrangement similar to the lattice structure of ionic peroxide

In ionic perovskite crystals, at least three ions with different radii are required to form a characteristic perovskite lattice
.

In contrast, Cherniukh et al.

In addition, the authors also found that for a system composed of CsPbBr3 nanocubes and Fe3O4 nanospheres, small changes in the relative size and fraction of the two nanocrystals can transform the resulting superlattice from a cubic arrangement to an ABO3 arrangement (Figure b)
.

High-resolution transmission electron microscopy and electron diffraction studies of these binary superlattices show that the orientation of the nanocubes is highly ordered

Superfluorescence has previously been observed in superlattices formed only by CsPbBr3 nanocubes
.

However, the periodicity, packing density, and flexibility of the orientation of the highly fluorescent CsPbBr3 nanocubes in the superlattice of Cherniukh and colleagues can be customized, opening up new avenues for the study of this phenomenon

[Conclusion and Outlook]

What is it? It seems feasible that the further expansion of the superlattice family is the next goal of this research field
.

Cherniukh et al.

This discovery may also help develop the application of superfluorescence, which has been observed in various atomic, molecular, and nanoscale systems, but has not yet been used in devices
.
The ability to customize the 3D structure of the superlattice may provide a way to arbitrarily customize the superfluorescence so that it can be used as, for example, a quantum light source
.
In turn, this may require further efforts to improve the three-dimensional order of the superlattice and increase the size of the material that can be prepared to strictly maintain the order
.
When the superlattice is integrated into a device, it may also be necessary to study stable ordered structures, possibly through the use of connecting molecules between nanocrystals
.

　　At the same time, the new discoveries have opened the way for researchers to try a variety of nanocrystals that have different properties—such as light-emitting, magnetic, or insulating properties—as the building blocks of superlattices
.
This may result in materials with multiple functions, all of which can be controlled by the spatial arrangement and distance between nanocrystals
.