Self-Hybridized Exciton-Polariton Photodetectors From Layered Metal-Organic Chalcogenolates

Abstract

Exciton-polaritons (EPs) arising from strong light-matter coupling offer new pathways for controlling optoelectronic properties. While typically requiring closed optical cavities for strong coupling, we demonstrate that 2D metal-organic chalcogenolates (MOCs), mithrene (AgSePh), with a high refractive index (~2.5) and strong excitons enable self-hybridized polaritons photodetectors (PDs) without top mirrors, simplifying device architecture. Through thickness-tuned multimode polariton engineering, we achieve photodetection of sub-bandgap photons via lower polariton states, validated through reflectance, photoluminescence (PL), and photocurrent spectroscopy with quantitative theoretical agreement. Trap-assisted two-photon absorption enables sustained strong coupling even under sub-bandgap excitation. The polariton dispersion yields ultrafast group velocities (~65 {\mu}m/ps), extending exciton diffusion lengths from hundreds of nanometers to several micrometers. Strong-coupling devices demonstrate a 2.38-fold enhancement in photo-to-dark current ratio compared to weak-coupling counterparts, establishing a practical route to polariton-enhanced photodetection and light harvesting.