A flexible PI/graphene heterojunction optoelectronic device modulated by TENG and UV light for neuromorphic vision system

Artificial neural visual electronic devices have attracted great research interest in the fields of low-power and high-efficiency pattern recognition. However, emulating the hyperpolarized behavior of cone and rod cells and further developing image recognition functionalities encounter formidable challenges due to the inherent optoelectronic effects in semiconductors. Here, a flexible optoelectronic synapse device based on polyimide (PI)/ Graphene heterojunction is proposed to effectively emulate human visual functionalities. The PI not only serves as a flexible substrate but also exhibits remarkable UV light absorption capability. Furthermore, the electrical conductivity of graphene channel can be bidirectionally regulated through UV light irradiation and triboelectric nanogenerator (TENG) induced negative gas ions adsorption, corresponding to inhibitory and excitatory behaviors, respectively. The negative photoconductance effect, stemming from the recombination between photogenerated electrons in PI and holes in graphene, endows the emulation of hyperpolarized behavior of cone and rod cells. Various synaptic behaviors, such as paired-pulse facilitation, spike-rate dependent plasticity, short-term depression, and long-term depression, can be achieved by modulating light pulses parameters. Additionally, the TENG-induced gas ions adsorbed on the graphene surface act as floating gate, leading to an increase in graphene conductivity. Continuous pulse stimulation through corona discharge enables long-term potentiation behavior in the synaptic device. Ultimately, combining opto-electrically coupled weight updates with artificial neural network algorithms allows for real-time handwritten digit recognition. This work presents a novel pathway for constructing simple flexible artificial visual electronic systems.

Automated summary

This study proposes a flexible optoelectronic synapse device based on polyimide/graphene heterojunction, which effectively emulates human visual functionalities and achieves various synaptic behaviors by modulating light pulses parameters. The conductivity of the graphene channel can also be regulated through TENG-induced negative gas ions adsorption, enhancing the functionality of the device.