Polymer–Fullerene Bulk Heterojunction-Based Strain-Sensitive Flexible Organic Field-Effect Transistor

In this work, we have fabricated organic field-effect transistor using the blend of poly(3-hexylthiophene) and [6,6]-phenyl C61-butyric acid methylester as active layer. Transistor was fabricated in MESFET-type configuration with top gate and bottom drain/source contacts on flexible PET substrate. Drain and source contacts were made using silver (Ag), whereas gate contact was made by depositing aluminium (Al) on the active layer. Active layer showed ohmic-type contact with drain/source electrodes and Schottky-type contact with gate electrode, which was discussed with the help of energy band diagram. Current–Voltage ( I – V ) characteristics of the transistor were found similar to p-type mode I – V characteristics of a typical low-voltage ambipolar field-effect transistor. Strain sensing properties of the device were investigated by bending it at 0° and 90° with respect to the direction of drain-to-source current for different strains of 1, 1.6, and 3.2 %. Significant proportional variation in the drain-to-source current was observed due to the bending from both sides; however, sensitivity of the device was found higher when strain was applied at 90° with respect to drain-to-source current. Sensitivity values were found to be equal to 0.18 and 0.65 μA/ % when a constant bending strain of 3.2 % was applied at 0° and 90° with respect to the direction of drain-to-source current, respectively.