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.
@article{arxiv.2602.23138,
title = {Engineering in-plane anisotropy in 2D materials via surface-bound ligands},
author = {Tomoaki Sakurada and Woo Seok Lee and Yeongsu Cho and Rattapon Khamlue and Petcharaphorn Chatsiri and Nicholas Samulewicz and Tejas Deshpande and Annlin Su and Peter Müller and Tadashi Kawamoto and Shun Omagari and Martin Vacha and Watcharaphol Paritmongkol and Heather J. Kulik and William A. Tisdale},
journal= {arXiv preprint arXiv:2602.23138},
year = {2026}
}