Abstract: Colloidal Cesium Lead Halide Perovskite nanocrystals (CsPbX3 NCs) exhibit spectrally narrow (<100 meV, 12-45 nm from blue-to-near-infrared) spontaneous and stimulated emission. Owing to their high oscillator strength, slow dephasing (long coherence times of up to 80 ps), minimal inhomogeneous broadening of emission lines, and a bright triplet exciton character with orthogonal dipole orientation, these NCs make for a highly versatile platform for creating controlled, aggregated states exhibiting collective phenomena. In this regard, NCs must be assembled into long-range ordered superlattices (SLs), the simplest case being simple cubic packing of cubic NCs. These SLs were found to exhibit sharp red-shifted lines in their emission spectra and superfluorescence (a fast collective emission resulting from coherent multi-NCs excited states).

We now present perovskite-type ABO3 binary and ternary NC SLs by a shape-directed co-assembly of, highly luminescent cuboid-shaped CsPbBr3 NCs (occupying B- and/or O-sites) with spherical dielectric Fe3O4 or NaGdF4 NCs (A-sites) and truncated-cuboid PbS NCs (B-site). Such ABO3 SLs, as well as other newly obtained SL structures (binary NaCl- and AlB2-types, columnar assemblies with disks etc.), exhibit a high degree of orientational ordering of CsPbBr3 nanocubes. 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.