Oral: Coulomb-Engineered Charge Localization in Hybrid Bilayer Crystal Transistors

Manipulating delocalized and localized charges in solids generates intriguing physical phenomena that lead to novel transport properties. However, most of such systems require bulky device design or critical measurement conditions. Here, we present a novel bilayer material platform that consists of a monolayer of MoS₂ and perylene diimide crystals. This 2D hybrid bilayer crystal (2D HBC) is only four-atom thick, has wafer scale uniformity, and is capable of charge injection and quantification. Proper band edge alignment allows simultaneous access across both the MoS₂ conduction band and PDI LUMO level. Under electrolyte gating, up to 3×10¹³ cm^-2 charges can be injected into PDI. Transport measurement reveals highly unusual negative transconductance (NTC) under room temperature. Optical reflectance measurement demonstrates electron depletion in MoS₂ and accumulation in PDI, giving rise to a transformation from delocalized to localized electrons across the bilayer. This phenomenon originates from the overscreening effect of charges in the PDI layer as the total charge density surpasses a threshold value. This anomalous behavior can be modeled by ion pairing formation between PDI^- and cations in the electrolyte, which greatly dampens the Coulomb repulsion between charges in PDI. Utilizing the unique single-band ambipolar transport property, we constructed integrated CMOS circuits and demonstrated an inverter operation.