Organic Heterojunction Phototransistors with Bi-Directional Photoresponse for Vision Biomimetics

The scientific community is very interested in artificial visual perception systems because of their neuromorphological capabilities, such as image recognition, learning, and memory. This study reports on an organic heterojunction ambipolar transistor with PTCDI-C8/C8-BTBT/PTCDI-C8 sandwich structure. The proposed transistor efficiently transports both holes and electrons, with a current-on-switch ratio of approximate to 106. Furthermore, hole or electron carrier transmission mechanisms are constructed to achieve the controllable adjustment of bi-directional photoresponse under identical light illumination conditions by adjusting the gate voltage (positive photoresponse for Vg = 30 V and negative photoresponse for Vg = -30 V). The basic synaptic behaviors are simulated under light illumination, and the power consumption of the device is 18.51 fJ per synaptic event, which is comparable to the energy required for biological synapses. Finally, the simulation of human visual adaptation is completed using the bi-directional photoresponse effects of the organic heterojunction phototransistor array, which provides a novel idea for neuromorphic visual simulation. This organic ambipolar heterojunction transistor is fabricated which can efficiently transport both holes and electrons, and a high Ion/Ioff ratio is observed. Bi-directional positive and negative photoresponses are achieved by adjusting the gate voltage. The simulation of visual adaptation is completed by using the bi-directional photoresponse effects of the organic heterojunction phototransistor array. image