Solution Processed Highly Uniform and Reliable Low Voltage Organic FETs and Facile Packaging for Handheld Multi-ion Sensing

Solution processed low power organic field effect transistors were fabricated on 10 cm × 10 cm size substrate with excellent uniformity (threshold voltage spread of 200 mV for more than 100 measured devices). A blend solution of small molecule organic semiconductor and polymer binder was deposited via a soft contact coating technique at a fast speed (20 mm/s) on photolith patterned fine resolution electrodes. With well controlled contact induced crystallization, highly uniform crystalline channels were obtained with low sub-gap density of states over large area for low voltage electrical behaviors (subthreshold swing of 80 mV/dec) and excellent uniformity. The devices also exhibit superior bias stress stability in all operational regimes. A facile packaging approach was further developed to connect the OFET electrodes to external wet test environment. Finally, a handheld battery powered OFET multi-ion (H
⁺
, Na
⁺
, K
⁺
) sensing system was demonstrated for point-of-care test.