The Synergy Effect of Al/Ti Electrodes on Effective Electron Injection for n-Channel Transistors and Ambipolar Complementary Circuits

This paper reports the utilization of cost-effective bottom-contact electrodes composed of aluminum (Al) and titanium (Ti) to facilitate efficient electron injection in n-channel organic transistors. The optimized Al/Ti electrode has a low work function of around 4.03 eV, combining the high conductivity of Al with the stable interface of Ti, making it highly suitable for the electrodes of n-channel transistors. Diketopyrrolopyrrole (DPP)-based polymeric semiconductor transistors with Al/Ti electrodes result in a notable enhancement of the n-channel performance while also leading to a significant decrease in the p-channel properties. The transmission-line method (TLM) and low-frequency noise (LFN) techniques are employed to quantitatively evaluate the effects of Al/Ti electrodes on the charge injection of n-channel OFETs. Finally, complementary inverters composed of different electrodes (Au as a p-channel and Al/Ti as an n-channel electrode) are demonstrated. The inverters showed high static and dynamic characteristics such as ideal voltage transfer curves (VTCs) with minimal hysteresis, high gain (∼25), high noise margins (68%), and low static power consumption (19.9 μW).