Low-voltage ambipolar phototransistors based on a pentacene/PC ₆₁BM heterostructure and a self-assembled nano-dielectric

Low-voltage ambipolar organic phototransistors based on a pentacene/[6,6]-phenyl-C61-butyric acid methyl ester heterostructure as the semiconducting layer and a self-assembled monolayer as the gate dielectric, are demonstrated. The transistors are shown to operate below |3| V with electron and hole mobilities on the order of 0.1 and 10^-3 cm²/Vs, respectively. Importantly the channel current is found to depend not only on the biasing conditions but also on the intensity of incident light, allowing the device to be used as an optical sensor. The external quantum efficiency and response time of these low-power phototransistors are calculated to be -0.8% and 210-225 ms, respectively. By integrating two such ambipolar phototransistors, low-voltage, light-sensitive complementary-like integrated circuits such as voltage inverters are also realised. The present results demonstrate the potential of organic phototransistors for low-power optoelectronic applications.