Slipping‐Free Halide Perovskite Supercrystals from Supramolecularly‐Assembled Nanocrystals

Abstract

AbstractSupramolecularly assembled high‐order supercrystals (SCs) help control the dielectric, electronic, and excitonic properties of semiconductor nanocrystals (NCs) and quantum dots (QDs). Ligand‐engineered perovskite NCs (PNCs) assemble into SCs showing shorter excitonic lifetimes than strongly dielectric PNC films showing long photoluminescence (PL) lifetimes and long‐range carrier diffusion. Monodentate to bidentate ligand exchange on ≈ 8 nm halide perovskite (APbX3; A:Cs/MA, X:Br/I) PNCs generates mechanically stable SCs with close‐packed lattices, overlapping electronic wave functions, and higher dielectric constant, providing distinct excitonic properties from single PNCs or PNC films. From Fast Fourier Transform (FFT) images, time‐resolved PL, and small‐angle X‐ray scattering, structurally and excitonically ordered large SCs are identified. An Sc shows a smaller spectral shift (<35 meV) than a PNC film (>100 meV), a microcrystal (>100 meV), or a bulk crystal (>100 meV). Also, the exciton lifetime (<10 ns) of an SC is excitation power‐independent in the single exciton regime 〈N〉<1, comparable to an isolated PNC. Therefore, bidentate‐ligand‐assisted SCs help overcome delayed exciton or carrier recombination in halide perovskite nanocrystal assemblies or films.