Competition in the hydrogen bonding network for the crystallization of low-dimensional hybrid perovskites using N-Methyl-2-Pyrrolidone solvent

Abstract

N-methyl-2-pyrrolidone (NMP), a solvent widely used for the preparation of high-quality 3D lead halide perovskite films, has been tested for the synthesis of new low-dimensional hybrid lead halide materials. While the synthesis using different primary amines in aqueous media afforded two-dimensional hybrid perovskites, the use of NMP as a solvent led to the formation of five non-perovskite compounds close to the 1D 2H perovskite crystallizing in the K₄CdCl₆-type structure. Structural analysis reveals that NMP hinders hydrogen bonding between –NH₃⁺ groups and the halide network with competing interactions leading to 1D non-perovskite structures in place of 2D perovskites. Under these conditions, NMP competes for H-bonding with –NH₃⁺ and systematically favored 1D iodoplumbate chains over 2D perovskites. Optical measurements confirm a bandgap increase consistent with reduced dimensionality.