Spatially resolved fluorescence of caesium lead halide perovskite supercrystals reveals quasi-atomic behavior of nanocrystals

Abstract

We correlate spatially resolved fluorescence (-lifetime) measurements with X-ray nanodiffraction to reveal surface defects in supercrystals of self-assembled cesium lead halide perovskite nanocrystals and study their effect on the fluorescence properties. Upon comparison with density functional modeling, we show that a loss in structural coherence, an increasing atomic misalignment between adjacent nanocrystals, and growing compressive strain near the surface of the supercrystal are responsible for the observed fluorescence blueshift and decreased fluorescence lifetimes. Such surface defect-related optical properties extend the frequently assumed analogy between atoms and nanocrystals as so-called quasi-atoms. Our results emphasize the importance of minimizing strain during the self-assembly of perovskite nanocrystals into supercrystals for lighting application such as superfluorescent emitters.

Superradiance and Exciton Delocalization in Perovskite Quantum Dot Superlattices

“…At room temperature, the PLQY values vary from SL to SL and are consistently lower than that of the isolated QDs, likely due to the increased probability of nonradiative energy transfer to defect sites in the SLs. 42,43 At low temperatures, the radiative rate in highly ordered SLs is enhanced by superradiance, which can outcompete nonradiative pathways and lead to PLQY close to 1.…”

Emergent properties in supercrystals of atomically precise nanoclusters and colloidal nanocrystals

“…14). 89 We self-assembled the SCs by simple solvent evaporation (see Fig. 5a and Section 2.2) and used diffraction-limited confocal laser scanning microscopy (Fig.…”

Printable assemblies of perovskite nanocubes on meter-scale panel

“…The bottom-up approach is primarily aimed at exploiting the emergent properties of NP assemblies that are notably different from those of the individual constituents or bulk materials (10)(11)(12)(13). These emergent properties have been experimentally confirmed after rationally controlling the interaction of interparticles, composition, stoichiometry, geometry, and crystal structure (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24). In these assembled structures, quantum effects can fundamentally change the properties of devices.…”