Tuning Electrode Work Function and Surface Energy for Solution Shearing High-Performance Organic Field-Effect...

A bottom-contact organic field-effect transistor (OFET) is easily adaptable to the standard lithography process because the contact electrodes are deposited before the organic semiconductor (OSC). However, the low surface energy of bare electrodes limits utilizing solution-processed single-crystal OSCs. Additionally, the bare electrode usually leads to a significant charge injection barrier, owing to its relatively low work function (WF). Here, we simultaneously improved the surface energy and WF of gold electrodes by conducting oxygen plasma treatment to achieve high-performance OFET based on solution-processed organic single crystals. We cultivated a thin layer of gold oxide on Au electrodes to increase the WF by ∼0.7 eV. The surface energy of Au electrodes was enhanced to the same as AlO dielectric surface, enabling the seamless growth of large-area C₈-BTBT (2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene) organic single-crystal thin films via solution shearing. This technique facilitates the production of high-performance OFETs with the highest carrier mobility of 6.7 cm² V^-1 s^-1 and sharp switching characterized by a subthreshold swing of 63.6 mV dec^-1. The bottom-contact OFETs exhibited a lower contact resistance of 1.19 kΩ cm than its F₄-TCNQ-doped top-contact control device. This method offers a straightforward and effective strategy for producing high-quality single-crystal OFETs, which are potentially suitable for commercial applications.