Area-scalable film preparation and blue excitonic photoluminescence of organic–inorganic hybrid 2D semiconductor AgSePh (Ph = C6H5)

Abstract

Organic–inorganic hybrid silver benzeneselenolate (AgSePh, Ph = C₆H₅) has been actively studied in recent years as a rejuvenated 2D layered multi-quantum well (multi-QW) semiconductor, whose monolayer is a single QW that bears a 2D semiconducting [SeAgSe] polymeric network sandwiched between two layers of organic phenyl rings through Se–C bond linkages. We report here the area-scalable preparation of AgSePh thin films and their multi-QW-derived optically controlled excitonic properties. The well-known silver mirror reaction enables us to prepare area-tunable silver films, which are then converted to high-quality polycrystalline AgSePh thin films with lateral sizes ranging from 2 cm × 2 cm to 10 cm × 10 cm by reacting with Ph₂Se₂ vapor via an ethanol-assisted thermal evaporation process. Both small-area and large-area AgSePh thin films exhibit room-temperature-resolved multiple excitonic absorption bands (X₁ at 2.71 eV, X₂ at 2.73 eV and X₃ at 2.81 eV) in the visible-spectral region, large exciton binding energy (E_b: ∼0.38 eV), and narrow-linewidth blue photoluminescence (PL) at 2.64 eV (∼470 nm). The quantum and dielectric effects arising from the multi-QW structure account for the presence of Coulomb-bound Wannier–Mott exciton states with different energy levels and high E_b, and especially the radiative recombination of the lowest-energy X₁ excitons leads to the blue PL emission. Furthermore, AgSePh thin films are found to show good PL stability and surface wettability for organic solvents (e.g., ethanol and toluene). These area-tunable, blue-emissive AgSePh thin films would find wide use in environment-friendly luminescent materials (Pb/Cd-free), optical (bio)imaging, light-emitting devices, quantum optics, and organic optoelectronic devices.