Why Do Perovskite Nanocrystals Form Nanocubes and How Can Their Facets Be Tuned? A Perspective from Synthetic Prospects

Lead halide perovskite nanocrystals have recently emerged as the workhorse in quantum dot research for their unprecedented high brightness and tunable colors in the most in-demand red–green–blue windows. In most cases, it was revealed that these nanocrystals typically retain the hexahedron cubic or platelet shape. This has been observed for all lead halide perovskites, including mixed halides and hybrid perovskites. Hence, the big question remains whether multifaceted nanocrystals other than nanocubes remained synthetically challenging or the material preferred to retain the stable cube structure with particular lead halide octahedra arrangements. Multifaceted nanocrystals have several advantages because these might trigger anisotropic growth, self-assembly, and oriented attachment and also generate more efficient adsorption sites for catalysis. Keeping all these issues in mind, this Perspective discusses several successes and challenges in facet tuning of these nanocrystals and provides several concepts in generating new facets during their synthesis.