Surface Termination, Morphology and Bright Photoluminescence of Cesium Lead Halide Perovskite Nanocrystals

Colloidal cesium lead halide perovskite nanocrystals (CsPbX3 PNC, X=Cl, Br, I) exhibit important optoelectronic properties that make them amenable for a plethora of applications. The origin of these properties, even for as-synthesized and unpurified PNCs, is however largely unknown. Electronic structure calculations are therefore essential to understand with atomistic detail the properties of these nanomaterials, however finding a model for PNCs that resembles the experiments is a challenging task. Essentially, the main problem is how to correctly terminate the PNC surface that comprises of a large fraction of the atoms that compose the nanocrystal and of ligands employed in the synthesis. Here, we construct nominally trap-free models for PNCs taking into account experimental conditions. With density functional theory we analyze the effect of size, shape and halide composition on the electronic structure of PNCs. We confirm that the PNC crystalline core exhibits an orthorhombic structure and we demonstrat...