Flexible N-channel organic phototransistor on polyimide substrate

We report a flexible photoresponsive organic field-effect transistor, phototransistor (OPT), based on a fluorinated copperphthalocyanine (F16CuPc) and polymer gate dielectric on a flexible polyimide substrate. Under light illumination, the device exhibited a photoresponsivity of 2.15 mA/W at VGS = 2 V and optical power of 5.66 mW/cm2. The current ratio (Iphoto/Idark) of the light to dark states was calculated to be around 300 at VGS = 2 V. Furthermore, the switching time of the phototransistor was found to be lower than 0.1 s. When the substrate was bent outward up to a bending radius of 4.4 mm, the device still showed photoresponsive field-effect characteristics. However, the photoresponsivity and Iphoto/Idark ratio decreased with decreasing bending radius. These results indicate that the present flexible OPT could potentially be used in optoelectronic device applications.