Brightening self-trapped exciton emission in 2D metal-organic chalcogenolates via argentophilicity-mediated anisotropic compression

An emerging class of two-dimensional semiconductor materials, metal-organic chalcogenolates (MOCs), have garnered significant attention due to the strong excitonic effects arising from their intrinsic soft, hybrid multiquantum-well structures. However, modifying excitonic transitions that strongly couple to the argentophilic networks and constructing their structure-property relationships in MOCs remain daunting challenges. Here, we use silver phenylselenolate (AgSePh) as a model system to manipulate excitonic behavior and uncover the fundamental photophysical mechanisms through pressure engineering. A bright broadband Stokes-shifted emission is observed in AgSePh crystals along with the disappearance of blue narrow emission upon compression, which is attributed to the pressure-induced carrier transformation from free exciton to self-trapping exciton states. The considerable compressibility of the Ag-Se inorganic monolayer, driven by weakly bound argentophilic interactions, generates pronounced argentophilic intralayer distortion while simultaneously enhancing exciton-phonon coupling and excitonic oscillator strength. This work demonstrates the remarkable tunability of excitonic properties in layered MOCs.