Threshold Voltage Stability of Copolymer-Based Lateral Drift Region Organic Field-Effect Transistors Under Ambient Air Conditions and Gate-Bias Stress

The impact of bias stability on the threshold voltage shift in copolymer lateral drift region organic field-effect transistors (LDR-OFETs) is examined. The fabricated LDR-OFETs feature a diketopyrrolopyrrole-based polymer (DPPT-TT) and a poly(methyl methacrylate) (PMMA) film as the semiconductor and gate dielectric layers, respectively. Under ambient air conditions, the LDR-OFETs maintain normal functionality without significant degradation for up to 4320 h of continuous exposure, demonstrating robust stability. However, LDR-OFETs under bias stress exhibit more pronounced degradation compared with those under atmospheric stress. Notably, negative and positive biases differently impact the threshold voltage shift, while their effect on breakdown voltage (BV) remains consistent. This distinct degradation behavior of copolymer-based LDR-OFETs is analyzed and elucidated, focusing on bias-stress effects. The trap state density between the organic dielectric layer and the organic semiconductor (OSC) layer is identified as a key factor contributing to the threshold voltage shift when subjected to electrical stress. The study highlights the exceptional resilience of fabricated copolymer OSC-based devices against degradation induced by ambient conditions and gate-bias stress, showcasing their potential for achieving reliable and commercially viable organic power devices.