Spontaneous Self‐Assembly of Perovskite Nanocrystals into Electronically Coupled Supercrystals: Toward Filling the Green Gap

Abstract

Self‐assembly of nanoscale building blocks into ordered nanoarchitectures has emerged as a simple and powerful approach for tailoring the nanoscale properties and the opportunities of using these properties for the development of novel optoelectronic nanodevices. Here, the one‐pot synthesis of CsPbBr 3 perovskite supercrystals (SCs) in a colloidal dispersion by ultrasonication is reported. The growth of the SCs occurs through the spontaneous self‐assembly of individual nanocrystals (NCs), which form in highly concentrated solutions of precursor powders. The SCs retain the high photoluminescence (PL) efficiency of their NC subunits, however also exhibit a redshifted emission wavelength compared to that of the individual nanocubes due to interparticle electronic coupling. This redshift makes the SCs pure green emitters with PL maxima at ≈530–535 nm, while the individual nanocubes emit a cyan‐green color (≈512 nm). The SCs can be used as an emissive layer in the fabrication of pure green light‐emitting devices on rigid or flexible substrates. Moreover, the PL emission color is tunable across the visible range by employing a well‐established halide ion exchange reaction on the obtained CsPbBr 3 SCs. These results highlight the promise of perovskite SCs for light emitting applications, while providing insight into their collective optical properties.