Fig. 1. (a), (b) The arrangement of transistors and the orientation of carrier motion within a synapse under varying gate voltages, both negative and positive. (c) The continuous increase in EPSC under negative gate voltage stimulation. (d) IPSC exhibits a gradual decline as the positive gate voltage magnitude increases from 4 to 10 V.

Fig. 2. (a) The stability of EPSC induced by red light. (b) The stability of EPSC induced by UV light. (c) The EPSC following training with red light and UV light. (d) The synaptic currents regulated by the light pulse counts. (e) Relationship between the increase in EPSC and pulse number. (f) The EPSC of the light pulse. (g) The training process of optical synapses, including learning, forgetting, and relearning.

Fig. 3. (a) The schematic illustration of skin sunburn caused by intense UV exposure. (b) The effects of varying UV exposure durations. (c) The effects of varying UV irradiation intervals. (d) The effects of varying numbers of UV pulses applied.

Fig. 4. (a) Light-electric-light stimulation. (b) Electric-light-electric stimulation. (c) Light-(light + electric)-light stimulation. (d)–(f) The corresponding peak current I30 for (a)–(c). (g) Schematic diagram of learning efficiency.