Nanoplatelet Superlattices by Tin-Induced Transformation of FAPbI3 Nanocrystals

The transition from 3D to 2D lead halide perovskites is traditionally led by the lattice incorporation of bulky organic cations. However, the transformation into a coveted 2D superlattice-like structure by cationic substitution at the Pb2+ site of 3D perovskite is unfamiliar. It is demonstrated that the gradual increment of [Sn2+] alters the FASn(x)Pb(1-x)I(3) nanocrystals into the Ruddlesden-Popper-like nanoplatelets (NPLs), with surface-absorbed oleic acid (OA) and oleylamine (OAm) spacer ligand at 80 degrees C (FA(+): formamidinium cation). These NPLs are stacked either by a perfect alignment to form the superlattice or by offsetting the NPL edges because of their lateral displacements. The phase transition occurs from the Sn/Pb ratio >= 0.011, with 0.64 wt% of Sn2+ species. At and above Sn/Pb = 0.022, the NPL superlattice stacks start to grow along [00l] with a repeating length of 4.37(3) nm, comprising the organic bilayer and the inorganic block having two octahedral layers (n = 2). Besides, a photoluminescence quantum yield of 98.4% is obtained with Sn/Pb = 0.011 (n >= 4), after surface passivation by trioctylphosphine (TOP).

Automated summary

The transition from 3D to 2D lead halide perovskites can be achieved by cationic substitution, resulting in a 2D superlattice-like structure. The phase transition occurs when the Sn/Pb ratio is equal to or greater than 0.011, forming a superlattice structure with organic bilayers and inorganic blocks. Additionally, high photoluminescence quantum yield can be obtained after surface passivation.