Performance and Reliability Improvement of Double-gate Structure-based Flexible PBTTT Organic Thin-film Transistors

Flexible organic thin-film transistors (OTFTs) offer intrinsic mechanical flexibility, low-temperature process compatibility, and large-area manufacturability, making them attractive platforms for next-generation wearable and conformable electronics. In this study, we compared single-gate (SG) and double-gate (DG) structures in poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT) channel-based flexible OTFTs and demonstrated the superiority of the DG structure in terms of mechanical and electrical stability, as well as long-term durability under constant electrical and mechanical stress conditions. In DG devices, the operation was controlled by the gate-bias configuration, enabling top-gate (TG), bottom-gate (BG), and double-gate (DG) operation. Under DG operation, the on/off ratio was approximately 50× higher than that under BG operation and ∼ 10× higher than that under TG operation, and the field-effect mobility was increased by ∼ 30× and ∼ 3×, respectively. The DG mode also exhibited the lowest subthreshold swing (SS) among the three modes. Because DG transistors use two gates to modulate the channel, they showed smaller variations in threshold voltage (Vth) and on-current under bending/curved conditions, compared to SG devices. These results indicate that the DG structure may help preserve device characteristics against mechanical and electrical stress. Furthermore, the DG devices exhibited tunable modulation of the drain current and Vth via gate-biasing, suggesting their potential for flexible electronic applications requiring controllable operation under mechanical bending. Overall, these results demonstrate that the DG structure is a robust design strategy for high-performance flexible OTFTs and offers practical guidelines for mechanically reliable organic electronics.