Scalable Processing of Low Voltage Organic Field Effect Transistors With a Facile Soft-Contact Coating Approach

A soft-contact coating (SCC) method, using a rotatable steel sheet as the meniscus guide, is developed for depositing organic semiconductors (OSCs). The method is used to fabricate bottom-gate bottom-contact organic-field effect transistors (OFETs) using blended solution of small molecule OSC and polymer binder. During the coating process, the meniscus guide maintains very weak contact force to the substrate surface, avoiding damages to the pre-fabricated electrodes. Even at a fast coating speed of 20 mm/s, well controlled crystallization can be achieved to form low sub-gap density of the states (DOS) channels for low voltage OFETs of excellent uniformity. The fabricated low voltage OFETs on plastic substrate in full solution processes exhibit high mobility reaching $1.5 ~{\text {cm}}^{{2}}\cdot \,\,\text{V}^{\text {-1}}\cdot \,\,\text{s}^{\text {-1}}$ , and a small threshold voltage dispersion less than 250 mV for measured 159 devices.