Charge Localization and Overscreening in Two-Dimensional Ion-Coupled Hybrid Bilayer Crystals

Recent advances in moiré lattices with tunable interlayer potentials have enabled observation and control of collective electronic phenomena. However, developing large-scale applications based on them remains difficult because of the extreme sample and experimental requirements, which originate from the relatively weak localization potential. Here, we report large-scale fabrication of hybrid bilayer transistors with strongly localized states that exhibit metal-insulator transistion under room temperature with tunable charge densities. Our transistors use four-atom-thick crystalline films synthesized with perylene molecular crystal atop MoS₂ monolayer, simultaneously hosting localized and delocalized electronic states. Upon electron doping by ionic gating, their electrical conductivity increases to a high peak value before dropping by two orders of magnitude; this coincides with a massive charge transfer from the delocalized to localized states reaching a high density up to 3×10¹³ per centimeter square. Our experiments show that this strong localization of injected carriers leads to an overscreening effect, which is driven by the drastic reduction of the Coulomb repulsion through the ion-pair formation. The different transconductance regimes in our bilayer transistors further enable an ambipolar operation within a single band, and we apply this to produce a complementary transistor device without substitutional doping. Our study reveals an uncharted working regime of two-dimensional hybrid crystals engineered with charge localization, unlocking the potential of strong Coulomb correlations for practical electronics applications.