Thermal Operational Stability in Organic Thin Film Transistors: The Critical Role of Interface Composition and Deposition Conditions

ABSTRACT The widespread adoption of organic thin‐film transistors (OTFTs) in flexible, wearable, and biodegradable electronics depends on achieving optimal electrical performance while ensuring reliable performance under typical environmental stressors such as humidity, oxygen, and heat. Among these, thermal stability remains underexplored, despite being critical for devices exposed to sterilization, body heat, or fluctuating environmental conditions. Here, we demonstrate that the thermal response of fluorinated silicon phthalocyanine (F 10 ‐SiPc) OTFTs can be rationally tuned by interfacial chemistry and deposition temperature, providing a scalable route to environmental robustness. By comparing octyltrichlorosilane (OTS), hexamethyldisilazane (HMDS), and plasma‐treated SiO 2 dielectrics with F 10 ‐SiPc films deposited at either 25°C or 100°C, we identify two distinct transport regimes. OTS promotes highly crystalline films with excellent room‐temperature mobility but exhibits non‐recoverable reduced performance at elevated operating temperatures, accompanied by increased post‐heating hysteresis, suggestive of dipole‐induced interfacial charge trapping. In contrast, HMDS and plasma yield more disordered morphologies that reorganize reversibly under heat, leading to mobility enhancements of 100%–800% via thermally activated hopping. Raising the deposition temperature lowers the initial mobility but reshapes the trajectory of thermal response. Together, these results establish interlayer selection and deposition temperature as complementary design parameters to deliberately program thermal stability profiles in OTFTs. This framework connects processing to operational reliability, advancing the design of organic electronics capable of surviving real‐world thermal and environmental demands without new materials or complex encapsulation.