Preparation of light-emitting organic field-effect transistors with asymmetric electrodes

Light-emitting organic field-effect transistors (LEOFETs) based on Poly [2-methoxy, 5-(2′-ethyl-hexoxy)-1, 4-phenylenevinylene] (MEH-PPV), α-sexithiophene (α-6T) and N,N′-Ditridecylperylene-3,4,9,10- tetracarboxylic diimide (PTCDI-C13) were prepared on a SiO ₂ gate insulator. The LEOFETs based on MEH-PPV and α-6T showed a p-type semiconducting behavior whereas PTCDI-C13 operated in n-type FET. Asymmetric electrodes of Au-Al were prepared by twice of photolithography and lift-off techniques, and by electroplating of Au onto Al electrode to improved device performances. The emission efficiency of the devices with Au/Cr-Al was approximately 20 times higher than that of the device with Au/Al-Au/Al electrodes at the gate and drain voltages of -100 V. The emission region was observed with an optical microscope. The emission region was found to be very homogeneous along the drain electrode, and it did not shift when the gate and drain voltages changed. Although the carrier injection was improved by using asymmetric electrodes, the number of the carriers injected from the drain electrode was still lower than that from the source electrode in the unipolar devices.