A Very-High Frequency Solution-Processed Organic Field-Effect Transistor With Improved Voltage-Normalized Frequency...

Achieving very-high (VHF) and ultra-high frequency (UHF) operation in organic field-effect transistors (OFETs) would expand their field of application to wireless communication. Such vision remains a major challenge, with OFETs mostly limited to High-Frequency bandwidth (3 - 30 MHz) due to intrinsic limitations, such as contact resistance and charge mobility, and fabrication-related parasitism, especially when adopting solution-based approaches. Here, we report on p-type OFETs exhibiting a frequency of transition (f_T) up to 135 MHz at V_gs = V_ds = -22 V, improving the voltage normalized f_T (f_T/V²) for VHF organic transistors with f_T > 100 MHz to 0.28 MHz V^-2. The devices were realized through a combination of direct-writing and solution-processing techniques employing an air-stable high-mobility semiconductor blend based on 2,7-dioctyl[1] benzothieno[3,2-b][1]benzothiophene (C₈-BTBT) and poly(indaceno-dithiophene-co-benzothiadiazole) (C₁₆IDT-BT). Femtosecond-laser sintering enabled submicron gate overlaps (∼ 0.4 µm), minimizing width-normalized parasitic gate capacitances (C_g/W ≈ 2.5 pF cm^-1). DC and AC device characteristics can be approximated using compact models, and theoretical simulations indicate that these OFETs could be potentially used to fabricate rectifiers with a -3 dB cut-off frequency of 200 MHz. These results represent a significant step toward high-speed organic electronics, establishing a pathway for wireless systems fabricated through scalable solution-based processes.