Ligand-Assisted Self-Assembly of 3D Perovskite Nanocrystals into Chiral Inorganic Quasi-2D Perovskites (n=3) with Ligand-Ratio-Dependent Chirality Inversion

Chiral inorganic quasi-2D perovskites are prepared by self-assembling 3D perovskites in solution for the first time. The quasi-2D perovskite synthesized is a pure-phase perovskite with < n > = 3 and is periodically arranged, which is a big breakthrough in quasi-2D inorganic perovskites. With the individual chiral CsPbBr3 nanocrystals (NCs) assemble into quasi-2D perovskite, the g-factor significantly improved (approximate to 5 x 10(-3)). In addition, the chiroptical activity of quasi-2D perovskites is explored to be improved with the lateral size increasing. In the first stage of assembly, chiral optical activity is increased due to the lateral size-dependent optical activity, while the changes in the later stages are attributable to the chiral morphology. Interestingly, chirality inversion is found to be correlated to the number of ligands. It is believed that different conformers of chiral ligands caused by steric hindrance of the original ligand oleylamine result in opposite circular dichroism (CD) polarities. The chirality inversion phenomenon is universal, regardless of the choice of ligands. This work opens up a new path for the synthesis of quasi-2D perovskites and provides more opportunities for the modulation of chiral optical activity.