fig2

Figure 2. Schottky junction-based zero-power optoelectronic synapses. (A) Schematic illustrations of the working mechanism in a Schottky junction-based zero-power optoelectronic synapse correspond to the (i) original, (ii) illumination, and (iii) dark state, respectively. E_c, E_v and E_F represent the bottom of conduction band, top of valence band, and Fermi level of the semiconductor, respectively. Φ_B0, V_bi and e denote the work function of metal, built-in potential and elementary charge, respectively; (B) Schematic of the Bi₂O₂Se-V_Se nanosheet-based zero-power optoelectronic synapse, with the inset highlighting the vacancy-rich atomic structure; (C) I_DS depending on V_DS characteristics of the device measured in dark conditions (top) and I_DS without bias under illumination at wavelengths of 350, 532, and 1,050 nm (P = 66 μW·cm^-2), demonstrating broadband photoreception (bottom); (D) Demonstration of high-pass filtering of the device. Subfigures (B-D) Reproduced with permission^[32]. Copyright 2024, American Chemical Society; (E) Schematic illustration of a 10 × 5 array of ITO/P3HT/Al zero-power optoelectronic synapse; (F) Representative PSCs induced by two consecutive light pulses (λ = 520 nm, P = 215 mW·cm^-2, duration = 100 ms, interval = 500 ms); (G) Photopic adaptation of the zero-power vision sensor array for pattern recognition. Subfigures (E-G) Reproduced with permission^[33]. Copyright 2025, American Chemical Society; (H) Schematic illustration of the Cs₂AgBiBr₆-based zero-power photonic synapse; (I) Representative EPSC triggered by 10 light pulses (λ = 445 nm, P = 36.6 μW·cm^-2) exhibiting in-sensor reservoir; (J) The weight modulation in the 25 × 4 array before and after the 50 training epochs for vehicle-flow classification. Subfigures (H-J) Reproduced with permission^[34]. Copyright 2022, John Wiley & Sons. Bi₂O₂Se-V_Se: Bi₂O₂Se nanosheet with selenium vacancies; ITO: indium tin oxide; P3HT: poly(3-hexylthiophene-2,5-diyl); PSCs: postsynaptic currents; EPSC: excitatory postsynaptic current; P(VDF-TrFE): poly(vinylidene fluoride-trifluoroethylene).