Quantitative Modeling of Self-Assembly Growth of Luminescent Colloidal CH₃NH₃PbBr₃ Nanocrystals

The organic–inorganic hybrid metal halide perovskites with different dimensions and diverse architectures are highly attractive materials for optoelectronic applications. However, people know little about the dynamics of their formation processes. Here, we study both experimentally and theoretically the self-assembly formation dynamics of the luminescent colloidal CH₃NH₃PbBr₃ nanocrystals. We have observed their successive transformations from original spherical quantum dots to periodically stacked nanoplatelets when the primitive colloidal nanocrystals with a high concentration were maintained in liquid for a prolonged period of time. A theoretical dynamic collision model by taking into account the popular van der Waals force, the polarization force that is unique for the perovskites, and the electrostatic forces between particle surfaces in the presence of the surface ligands is proposed to explain the self-assembly process of the colloidal CH₃NH₃PbBr₃ nanocrystals. The result reveals that the rather easy self-assembly of the organic–inorganic hybrid perovskites with different morphologies in the absence of enough surface ligands is closely related to their intrinsic polarization force, whereas the presence of the surface ligands could hamper the self-assembly process. The proposed theoretical model is general and can be used to analyze the self-assembly dynamics of various types of colloidal nanostructures.