Efficient in-Plane Exciton Transport in a Discontinuous Layered Lead-Bromide Perovskite.

Abstract

This study reports a new class of two-dimensional lead-bromide perovskite based on monovalent 4-aminomethylbenzoic acid (AMBA) cations featuring a discontinuous inorganic layer. Strong hydrogen-bonding interactions at the interlayer between AMBA molecules impose structural rigidity that prevents the formation of continuous metal-halide layers, instead generating isolated linear islands of three edge-sharing [PbBr6]4 - octahedra (Pb3Br14). The anisotropic in-plane arrangement of the structure is confirmed by angle-resolved polarized Raman spectroscopy, which reveals directional vibrational modes aligned with the octahedral island orientation. Despite the discontinuous lattice, transient photoluminescence microscopy demonstrates efficient in-plane exciton transport. Transport is strongly anisotropic, with the diffusion coefficient along the c-axis (0.149 cm2/s) exceeding that along the a-axis (0.042 cm2/s) by over threefold. This anisotropy is attributed to preferential near-field resonant energy transfer between the anisotropically oriented islands, as confirmed by numerical simulations, offering an efficient alternative transport mechanism in discontinuous layered perovskites.