Highly Luminescent Lead Halide Perovskite Nanocrystals—From Synthesis Advancements to Multicomponent Superlattices

Colloidal lead halide perovskite nanocrystals (LHP NCs_,NCs, A=Cs⁺, FA⁺, FA=formamidinium; X=Cl, Br, I) have become a research spotlight owing to their spectrally narrow (&lt;100 meV) fluorescence, tunable over the entire visible spectral region of 400-800 nm, as well as facile colloidal synthesis. These NCs are attractive single-photon emitters as well as make for an attractive building block for creating controlled, aggregated states exhibiting collective luminescence phenomena. Attaining of such states through the spontaneous self-assembly into long-range ordered superlattices (SLs) is a particularly attractive avenue. In this regard also the atomically-flat, sharp cuboic shape of LHP NCs is of interest, because vast majority of prior work had invoked NCs of rather spherical shape. Long-range ordered SLs with the simple cubic packing of cubic perovskite NCs exhibit sharp red-shifted lines in their emission spectra and superfluorescence (a fast collective emission resulting from coherent multi-NCs excited states). When combined with spherical dielectric NCs, perovskite-type ABO₃ binary NC SLs form, wherein CsPbBr₃ nanocubes occupy B- and/or O-sites, while with spherical dielectric Fe₃O₄ or NaGdF₄ NCs reside on A-sites. When truncated-cuboid PbS NCs are added to these systems, ternary ABO₃-phase form (PbS NCs occuoy B-sites). Such ABO₃ SLs, as well as other newly obtained SL structures (binary NaCl- and AlB₂-types, columnar assemblies with disks <i>etc.</i>), exhibit a high degree of orientational ordering of CsPbBr₃nanocubes. These mesostructures exhibit superfluorescence as well, characterized, at high excitation density, by emission pulses with ultrafast (22 ps) radiative decay and Burnham-Chiao ringing behaviour with a strongly accelerated build-up time.