Solution-processable assembly of 2D semiconductor thin films and superlattices with photoluminescent monolayer inks

The controllable and precise synthesis of two-dimensional (2D) semiconductor thin films and superlattices with arbitrary thickness and composition (e.g., selective production of pure monolayer, bilayer, trilayer, and more) has been a long-standing challenge for both vapor-based chemical vapor deposition and solution-based methods. Here, we report the solution-processable layer-by-layer assembly of 2D thin films with precisely controlled thickness down to atomic scale (e.g., 1-10 layers and more for MoS2) using high-purity 2D monolayer ink materials. We have realized the general and scalable synthesis of high-quality photoluminescent 2D semiconductor monolayers in solution phase, including MoS2, MoSe2, WS2, WSe2, and others (monolayer purity > 98%), which even exhibit liquid-state fluorescence (e.g., 658 nm for MoS2 and 746 nm for WSe2). Furthermore, we have ink-printed photoluminescent MoS2/Ca2Nb3O10 thin-film superlattice with visible light emission. At last, this strategy is general for solution-processable assembly of versatile multilayer inorganic/inorganic and organic/inorganic superlattice materials, including InSe/In2Se3, NbS2/PVP/MoS2, TaS2/PVP/THAB/In2Se3, and others.