Organic–Inorganic Composite Dielectrics for Flexible C8-BTBT Thin-Film Transistors with Enhanced Molecular Ordering and Low-Voltage Operation

Flexible thin-film transistors (TFTs) are key components in flexible electronics. Here, we report a solution-processed composite dielectric designed to overcome the long-standing trade-off among dielectric constant, mechanical flexibility, and channel-orientation control. The incorporation of ZrO2 into the cross-linked poly(4-vinylphenol) (PVP) matrix increases the dielectric constant to ∼15, suppresses leakage current, and improves film uniformity while preserving flexibility. At the same time, the increased surface free energy and reduced surface roughness of the composite dielectric create a more favorable interface for the ordered growth of C8-BTBT. As a result, the organic semiconductor film exhibits improved crystalline orientation and reduced disorder-related interfacial trapping, leading to more efficient charge accumulation and charge transport. C8-BTBT TFTs based on the composite dielectric operate at low voltages (≤5 V) and deliver a high field-effect mobility of 5.8 cm2/V·s, while retaining over 90% of their initial performance after repeated bending. In addition, flexible inverter circuits and ring oscillators are successfully demonstrated with low power consumption and stable operation. These results highlight organic–inorganic composite dielectrics as an effective strategy for simultaneously optimizing dielectric properties, semiconductor ordering, and mechanical robustness, providing a viable pathway toward low-power flexible integrated electronics.