Structure‐Guided Balancing of Ambipolar Transport Enables Symmetric Switching in Heterojunction Bilayer Organic Transistor Inverters

ABSTRACT High inverter performance in ambipolar organic electronics requires balanced channel strengths rather than maximized single‐carrier mobility. Here, we demonstrate symmetric switching through balanced ambipolar transport in vertically stacked pentacene/ N , N ′‐ditridecylperylene‐3,4,9,10‐tetracarboxylic diimide (PTCDI‐C 13 ) heterojunction bilayers (HJBs) fabricated on polymer‐grafted SiO 2 dielectrics. By systematically tuning the nominal equivalent (1–4 monolayers, ML s) and thermal reorganization of the PTCDI‐C 13 underlayer, a structural symmetry window is identified in which intermolecular self‐assembly stabilizes both carrier mobility and threshold‐voltage alignment. Under optimized conditions (3 ML , 150°C annealed), nearly identical hole and electron mobilities (∼1.0 cm 2 V − 1 s − 1 ) and convergent threshold voltages enable complementary‐like inverters exhibiting high voltage gain (>200) and large noise margins under ±80 V operation. At absolute supply voltage (| V DD |) = 80 V, the extracted low‐ and high‐state noise margins are approximately 29.9–33.9 V, corresponding to approximately 75–85% of | V DD |/2. Notably, imbalanced charge transport degrades switching symmetry despite improved unipolar mobility, revealing a non‐monotonic relationship between molecular ordering and circuit performance. These results establish interface‐mediated self‐assembly as a structure‐guided route for engineering transport symmetry in organic HJBs, while broader material generality and manufacturing scalability remain to be established.