Gate Dependent Tunable Photosensitivity of Copper Phthalocyanine Based Organic Field Effect Transistors

Abstract

Organic field effect transistor (OFET) based photodetector with high sensitivity was fabricated using copper phthalocyanine (CuPc) as photoactive channel for weak light detection. The device fabrication was conducted at room temperature using thermal evaporation technique. The opto-electrical properties of the devices under dark and light conditions are studied in this work. The performance of the photodetector depends on the incident wavelength and the intensity of the incident monochromatic light. We also show that the photoresponse could be tuned by the gate bias, which offers an additional benefit for practical applications. The transfer characteristics of the devices appear to enhance under light illumination. A slight enhancement in the carrier mobility was also detected upon illumination. Similarly, the subthreshold swing has been reduced from 1.31 ± 0.18 V/decade under dark condition to 0.76 ± 0.12 V/decade under illumination. Further impact of gate voltage on responsivity, on/off ratio and detectivity was also studied for the proposed device. The maximum photosensitivity and responsivity obtained from these OFET based photodetectors was 237.21 ± 8.02 and 7.77 ± 0.17 A/W respectively at a power density of 1 mW/cm2 while operating at an input voltage of 4 V and bias voltage of -5 V. Also, a maximum detectivity of 1.38 ± 0.03×1012 Jones was obtained under the same operating condition. The high sensitivity, good stability, low noise and fast response towards weak light with different wavelength imply that OFET based photodetectors are particularly suitable for photodetection in the visible region of electromagnetic spectrum.