Operationally Stable Organic FETs with Bilayer Dielectrics on Low-Cost Flexible Polyimide Substrate

Organic FETs (OFETs) with bilayer dielectric poly(4-vinylphenol) (PVP)/HfO2 and polyvinyl alcohol (PVA)/HfO2 were fabricated on a flexible low-cost Kapton tape substrate with TIPS-pentacene:polystyrene as an active layer. The devicesexhibited average andmaximum field-induced mobility of 0.25(±0.10) and 0.37 cm2Vcm-1 scm-1 for PVP/HfO2 devices, and 0.35(±0.18) and 0.69 cm2Vcm-1 scm-1 for PVA/HfO2 devices, respectively, with low threshold voltage and I ON to I OFF ratio approaching 104 for both types of devices. Overlapping transfer multiple scans with very less performance variation under ambient conditions were observed. The devices were found to be fairly stable even when electrical stress was applied after a period of 5 months. Devices exhibited small degradation in I DS and small ΔVTH with high degree of reliability and small performance spreads under combined effects of ambient exposure over a period of 5 months and successive electrical stress. In addition, inverter based on these OFETs with external load was also demonstrated.