Halide perovskite nanocrystal self-assembly in micrometer-sized 3D hollow templates

Highly ordered halide perovskite nanocrystal (NC) assemblies, namely superlattices (SLs), have attracted significant attention, owing to their extraordinary optical characteristics, i.e., bright superfluorescent emission. However, the primary preparation method of perovskite NC SLs lacks controllability over position and size of SLs, wherefore integrating SLs into device structures such as photonic microcavities has been challenging. Here, we demonstrate template-assisted self-assembly to deterministically place and shape NC SLs. We observed that these assemblies exhibit similar signatures of superfluorescence as spontaneously assembled SLs. Our results are an important step for optical devices harnessing perovskite NC SLs.