Crystal Structure of Individual CsPbBr Perovskite Nanocubes.

The atomic structure of CsPbBr nanocubes (NCs) was studied at the single-particle level via a high-resolution transmission electron microscopy (HRTEM) defocus-series analysis. The technique entails acquiring lattice-resolved HRTEM images of individual NCs over progressive defocus values. CsPbBr NC atomic structure was evaluated by comparing acquired experimental data to simulated lattice-resolved images and corresponding Fourier transform patterns of both orthorhombic ( Pnma) and cubic ( Pm3̅m) CsPbBr polymorphs. Herein, CsPbBr NCs with average edge lengths ( l) of l ∼ 10 and 5 nm are analyzed using the aforementioned technique. In the former, we find evidence for the coexistence of both cubic and orthorhombic lattices. In the latter, solely cubic character is observed, illustrating a potential size dependency to the crystal symmetry of CsPbBr NCs. Such structural measurements provide critical insight into elucidating the structure/(optical and electrical) function relationship of CsPbBr NCs.