Ultrafast photoluminescence dynamics in templated self-assemblies of perovskite nanocrystals

Highly ordered nanocrystal (NC) assemblies, namely superlattices (SLs), have been investigated as a building block of novel bright (quantum) light sources because of their unique collective emission process, so-called superfluorescence. Thus far, the primary preparation method for perovskite NC SLs has been drying-mediated self-assembly, in which the NCs spontaneously assemble into SLs while the solvent evaporates. However, this method does not give control over the position and size of assemblies. Hence, it has been challenging to place NC assemblies in photonic device structures. Here, we demonstrate template-assisted self-assembly of CsPbBr3 NCs to achieve precise control of the geometrical features of NC assemblies. A solution of NCs is drop-casted on a substrate with hollow, lithographically-defined template structures made from SiO2. We allow slow solvent evaporation and remove excess NCs from the substrate surface afterward. Thus, NCs only remain in the templates, and the position and size of these NC assemblies can be controlled by changing the design of the hollow structures. We performed time-resolved photoluminescence measurements on these NC assemblies and observed signatures of collective photon emission. Our results provide an important step forward for the development of optical devices that harness embedded perovskite NC assemblies.