Template-Assisted Assemblies of Halide Perovskite Nanocrystals

Highly ordered colloidal nanocrystal (NC) assemblies, namely superlattices (SLs), have been explored for novel optical and optoelectronic devices because of their emergent properties arising from interactions between NCs. In particular, lead halide perovskite NC SLs have attracted significant attention owing to the combination of the extraordinary optical characteristics of individual NCs and the unique collective emission processes such as superfluorescence (SF) [1,2]. 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 slowly evaporates. Although this method is easy to implement, it lacks control of position and size of SLs. Therefore, it is challenging to place NC SLs in photonic structures like microcavities and realize NC SL based devices. Here, we demonstrate template-assisted self-assembly of CsPbBr3 NCs to achieve geometry control of SLs [3]. NC SLs are formed through drying-mediated assembly on a substrate with hollow template structures, which are fabricated with a similar method as developed for templates in inorganic-semiconductor growth [4]. The templates are made of SiO2 and have lateral dimensions of a few micrometers and 220 nm height. After drop-casting a solution of NCs, we allow slow evaporation of the solvent and remove excess NCs from the substrate surface afterwards. Since NCs only remain inside the templates, the position and size of these NC SLs are defined by the design of the hollow template structures. We conduct microscopic photoluminescence (PL) spectroscopy of these template-assisted NC SLs to evaluate the homogeneity and quality of the assemblies. Moreover, we perform time-resolved luminescence measurements, where we observe signatures of cooperative emission. Our result is an important step towards the development of optical devices that harness embedded perovskite NC SLs.

References [1] G. Rainò et al., Nature 563, 671 (2018) [2] I. Cherniukh et al., Nature 593, 535 (2021) [3] E. Kobiyama et al., ACS Nano 19, 6748 (2025) [4] H. Schmid et al., Applied Physics Letters 106, 233101 (2015) Acknowledgments We acknowledge H. Schmid for useful discussions and the IBM BRNC team for help with the fabrication. This work was supported by the Swiss National Science Foundation (Grant No. 200021_192308, "Q-Light - Engineered Quantum Light Sources with Nanocrystal Assemblies" and Grant No. 200021-231778, “Cavity-Enhanced Many-Body Interactions in Deterministically Positioned Perovskite Quantum Dots (CHIP-QD)”.