Highly textured crystalline films enabled by supercooling for short-channel vertical organic field-effect transistors exhibiting high on/off ratios
Fangcong Zhang, Hang Liu, Shunhong Dong, Lingxiang Zhang, Hangyuan Cui, Weida Chen, Sheng Zhuo, Wenwu Zhou, Pengfei Zhang, Zhuyuan Wang, Huiting Fu, Changjin Wan, Qingdong ZhengAbstract
Vertical organic field-effect transistors (VOFETs), where the channel length is determined by the thickness of the semiconductor, show great potential for future electronic devices. However, fabricating high-performance VOFETs with channel lengths of just a few tens of nanometers remains challenging, because ultrathin active layer is prone to leakage currents and electrical shorting. Here, a supercooling-assisted crystallization strategy is proposed to fabricate highly textured ultrathin C8-BTBT crystalline films for short-channel VOFETs. Compared with conventional slow-crystallization methods, this strategy stabilizes the preferred molecular orientation during crystallization, yielding highly ordered crystalline films with improved molecular tilt and enhanced vertical charge transport. By integrating these films with a self-assembled graphene source electrode, VOFETs with channel lengths as short as 25 nm were successfully fabricated. The optimized devices with a 50 nm-thick semiconductor layer exhibited an on/off ratio close to 109 and a current density of 137.15 mA cm⁻2. Furthermore, the excellent film uniformity enabled consistent device arrays with a density of 2500 units cm⁻2, providing a feasible route toward high-density, solution-processed small-molecule organic integrated circuits.