LAUSR

2D metal organochalcogenides (MOCs) are emerging hybrid organic–inorganic semiconductors with exciting properties, including strong exciton binding energy, polarized luminescence, in‐plane anisotropy, and record‐high exciton‐polariton coupling. However, existing synthesis methods struggle to deliver high‐quality materials with fast reaction time, high yield, and easy device integration. Herein, hot‐injection synthesis is introduced to produce silver phenylselenide (AgSePh) nanocrystals, a prototypical MOC, in 15 s, with a ≈70% yield and scalability of 0.4 grams. These nanocrystals remain colloidally stable in polar solvents for >4 weeks and can be spin‐coated into films for device applications. High‐resolution electron microscopy and X‐ray diffraction confirm their crystallinity and purity, while optimization of solvent viscosity, time, concentration, and temperature allow control of nanocrystal size from 50 nm to 10 µm. This synthesis approach is extendable to MOCs with other chalcogen compositions, enabling bandgap tuning across the visible spectrum. Thermogravimetric analysis shows thermal stability above 200 °C, and 77Se nuclear magnetic resonance spectroscopy suggests a nucleophilic substitution reaction. UV–vis absorption, photoelectron yield, and Kelvin probe measurements indicate p‐type behavior, and AgSePh exhibits a hole mobility of 4.88 × 10−2 cm2 V−1 s−1, outperforming many organic and hybrid materials and rivaling commonly used inorganic hole‐transporting materials like CuSCN and NiOx in thin‐film electronics.