Perovskite nanocrystal self-assemblies in 3D hollow templates

TL;DR

This paper introduces a template-assisted self-assembly method for creating ordered perovskite nanocrystal superlattices with controlled geometry, enabling improved integration into optical devices and studying collective emission phenomena like superfluorescence.

Contribution

It presents a deterministic approach to assemble perovskite nanocrystals in predefined geometries using lithographically-defined templates, overcoming randomness of traditional methods.

Findings

Successful control of nanocrystal superlattice placement and size.

Observation of superfluorescence signatures in the assembled structures.

Potential for tailored optical properties in device applications.

Abstract

Highly ordered nanocrystal (NC) assemblies, namely superlattices (SLs), have been investigated as novel building blocks of optical and optoelectronic devices due to their unique properties based on interactions among neighboring NCs. In particular, lead halide perovskite NC SLs have attracted significant attention, owing to their extraordinary optical characteristics of individual NCs and collective emission processes like superfluorescence (SF). So far, the primary method for preparing perovskite NC SLs has been the drying-mediated self-assembly method, in which the colloidal NCs spontaneously assemble into SLs during solvent evaporation. However, this method lacks controllability because NCs form random-sized SLs at random positions on the substrate rendering NC assemblies in conjunction with device structures such as photonic waveguides or microcavities challenging. Here, we demonstrate template-assisted self-assembly to deterministically place perovskite NC SLs and control their geometrical properties. A solution of CsPbBr3 NCs is drop-casted on a substrate with lithographically-defined hollow structures. After solvent evaporation and removal of excess NCs from the substrate surface, NCs only remain in the templates thereby defining the position and size of these NC assemblies. We performed photoluminescence (PL) measurements on these NC assemblies and observed signatures of SF, similar as in spontaneously assembled SLs. Our findings are crucial for optical devices that harness embedded perovskite NC assemblies and prepare fundamental studies on how these collective effects can be tailored through the SL geometry.