Side ionic-gated perovskite/graphene heterojunction synaptic transistor with bipolar photoresponse for neuromorphic computing

By combining the good charge transport property of graphene and the excellent photo-carrier generation characteristic of perovskite nanocrystal, we propose and demonstrate an ionic-gated synaptic transistor based on Cs PbBr3∕graphene heterojunction for bipolar photoresponse. Controlling the potential barrier of the Cs PbBr3∕graphene heterojunction by the ionic-gate of the electrical double-layer effect can promote the separation of photogenerated carriers and effectively retard their recombination. Using the ionic-gate-tunable Fermi level of graphene and the pinning effect of perovskite nanocrystal, the bipolar photocurrent responses corresponding to the excitatory and inhibitory short-term and long-term plasticity are realized by adjusting the negative gate bias. A series of synaptic functions including logic operation, Morse coding, the optical memory and electrical erasure effect, and light-assisted re-learning have also been demonstrated in an optoelectronic collaborative pathway. Furthermore, the excellent optical synaptic behaviors also contribute to the handwritten font recognition accuracy of ～95% in artificial neural network simulations. The results pave the way for the fabrication of bipolar photoelectric synaptic transistors and bolster new directions in the development of future integrated human retinotopic vision neuromorphic systems.