Jonas L. Hiller, Robert Thalwitzer, Ata Efekan Bozkurt, Ross Ewan Carter, Theresa Hettiger, Markus Fröhlich, Richard Hodak, Matheus Gomes Ferreira, Martin Eberle, Ekaterina Kneschaurek, Gerard N. Hinsley, Bihan Wang, Kuan Hoon Ngoi, Elke Nadler, Wojciech Roseker, Fabian Westermeier, Michael Sprung, Dmitry Baranov, Jannika Lauth, Frank Schreiber, Ivan A. Vartanyants, Marcus Scheele, Ivan Zaluzhnyy
Supercrystals of lead-halide perovskite nanocrystals combine the semiconducting properties of bulk perovskites with quantum confinement effects and extend them to the macroscopic scale. Supercrystals assembled via a two-layer phase diffusion process using an acetonitrile antisolvent were recently shown to be unusually robust. We investigate how the acetonitrile-assisted self-assembly process influences surface chemistry, the atomic lattice of nanocrystals, and the structure of the supercrystal. Using quantitative NMR spectroscopy, nanofocused X-ray diffraction, and optical spectroscopy, we show that a reduced density of the ligand shell caused by the exposure to acetonitrile in the assembly underlies the mechanical robustness of these supercrystals. Ligand stripping further drives a highly size-selecting lateral growth of the supercrystal and induces anisotropic relaxation of the nanocrystal atomic lattice while preserving the electronic coupling and robust light-emitting properties of the assembly. That enables the mechanical manipulation of supercrystals such as stacking, thereby opening new avenues for integration into optoelectronic devices.