The photoresponsive organic field-effect transistors based on copper phthalocyanine

Organic field-effect transistors (OFETs) based on copper phthalocyanine were fabricated and their current-voltage characteristics were measured in dark/under illumination. The results showed that OFETs with Au as source/drain electrodes exhibited a photo-current/dark-current ratio of 0.4 and a photoresponsivity of 2.55 mA/W under illumination by a laser diode with a wavelength of 655 nm and power density of 100 mW/cm 2; however, OFETs with Al as source/drain electrodes exhibited a photo-current/dark-current ratio up to 10 4 and a much lower photoresponsivity of 0.39 mA/W under the same conditions. The tremendous increase of photo-current/dark-current ratio is ascribed to the decrease of dark-current caused by Schottky contacts between Al source/drain electrodes and CuPc.