Engineering in-plane anisotropy in 2D materials via surface-bound ligands

TL;DR

This paper presents a method to induce and control in-plane anisotropy in 2D hybrid semiconductors through surface ligand modification, significantly altering their electronic and optical properties for advanced device applications.

Contribution

It introduces a novel ligand engineering strategy to tune in-plane anisotropy and optoelectronic properties in 2D silver phenylchalcogenide semiconductors, expanding material design options.

Findings

Pronounced in-plane electronic anisotropy in fluorinated derivatives

Direct-to-indirect bandgap transition in chlorinated variants

10x increase in photoluminescence quantum yield with fluorination

Abstract

2D materials exhibiting in-plane anisotropy enable novel functionality in electronic, optoelectronic, and photonic devices, yet their availability is generally limited to naturally-occurring low-symmetry van der Waals compounds. Here, we demonstrate an approach to structural engineering in a family of blue-emitting 2D silver phenylchalcogenide semiconductors based on steric interactions among surface-bound organic molecular ligands. By strategically halogenating specific sites of phenyl ligands, we demonstrate dramatic changes to the inorganic AgSe plane in mithrene (silver phenylselenolate, AgSePh). Density functional theory revealed pronounced in-plane electronic anisotropy for direct-gap fluorinated derivatives, while a chlorinated variant exhibited a direct-to-indirect bandgap transition. Furthermore, some fluorinated variants displayed strongly polarized absorption and luminescence, accompanied by a 10x enhancement in photoluminescence quantum yield. This work establishes a versatile approach for tailoring optoelectronic properties in hybrid semiconductors that is difficult or impossible to achieve in all-inorganic materials alone, offering new opportunities in advanced material design.