Fig. 1. (Color online) Flexible optomemristor based on C₂₇H₃₀O₁₅/FeO_x heterostructure. (a) Purple lotus solution prepared from lotus flowers, with the molecular structure of C₂₇H₃₀O₁₅ lotus in the switch functional layer of the optoelectronic memristor below. (b) Diagram illustrating the simulation of synapses and device structure of the Au/C₂₇H₃₀O₁₅/FeO_x/ITO memristor. (c) I−V characteristic curves of the Au/C₂₇H₃₀O₁₅/FeO_x/ITO optoelectronic memristor under light and dark conditions, showing a significant positive light effect with increased current density under light exposure. (d) Optical bandgap energy fitting comparison of FeO_x and C₂₇H₃₀O₁₅/FeO_x UV−Vis (Ultraviolet–visible) spectra. (e) Double logarithmic SCLC mechanism fitting under HRS state of the device. (f) Calculation of defect concentration at different I − V scan cycles (iterations) under HRS state. (g) Diagram illustrating the Au/C₂₇H₃₀O₁₅/FeO_x/ITO flexible memristor at different curvature radii.

Fig. 2. (Color online) Electrical characteristics of Au/C₂₇H₃₀O₁₅/FeO_x/ITO. (a) Resistance modulation of Au/C₂₇H₃₀O₁₅/FeO_x/ITO memristor under different bias scan voltages. (b) Modulation of memory behavior with different bias voltage scan rates. (c) I−V characteristic curves of C₂₇H₃₀O₁₅/FeO_x memristor tested after bending at a 60^° angle for 1, 10¹, 10², 10³, 10⁴ times, demonstrating excellent resilience of the flexible device to various bends. (d) Cycle endurance test of the memristor, with Au/C₂₇H₃₀O₁₅/FeO_x/ITO memristor achieving at least 10³ scan cycles. (e) Duration of high resistance state (HRS) and low resistance state (LRS) at V_read = 0.3 V. (f) 32 non-volatile multi-conductive states lasting 300 s, capable of achieving at least 5-bit computational accuracy. (g) Device-to-device stability. (h) Double logarithmic SCLC mechanism fitting in device LRS state. (i) Calculation of defect density at LRS state under different I − V scan cycles (iteration counts).

Fig. 3. (Color online) Optical Characteristics of Au/C₂₇H₃₀O₁₅/FeO_x/ITO. (a) Under light conditions, the cycle endurance of the Au/C₂₇H₃₀O₁₅/FeO_x/ITO memristor reaches up to 10³ cycles. (b) Light pulse intensity modulates the photoconductive state of the C₂₇H₃₀O₁₅/FeO_x memristor. (c) Light pulse width modulates the photoconductive state of the C₂₇H₃₀O₁₅/FeO_xmemristor. (d) At different light intensities, the photocurrent shows a linear correlation with frequency. (e) and (f) Gradual linear adjustment of 150 photoconductive states has the potential to achieve a calculation accuracy of 7 bits. Use a light pulse (19 mW, 0.5 s) (upper part of Fig. 3(f)) to stimulate the device, 150 photoconductive states were obtained, as shown in Fig. 3(e). In order to further observe the 150 stable states of photoconductivity, the photoconductivity stabilized by applying light pulses to (e) was amplified to obtain (f). From (f), it can be seen that the photoconductivity state of the flexible device can be maintained for at least 16 s, indicating stability. (g) Under light pulses (19 mW, 0.5 s), the analog memristor exhibits a time-dependent photocurrent response. Adjusting the number of light pulses enables transitions from STP to LTP. (h) Characteristics of paired-pulse facilitation (PPF) in the Au/C₂₇H₃₀O₁₅/FeO_x/ITO memristor under light pulses (64.6 mW) at intervals (0.5−13 s) . (i) Electro−optical synergy conductivity update. The conductivity is increased from low to high using ten light pulses (19 mW, 0.5 s), and decreased from high to low using four negative voltage pulses (−0.1 V, 0.5 s).

Fig. 4. (Color online) Digital speech signal recognition system based on flexible optoelectronic memristors Au/C₂₇H₃₀O₁₅/FeO_x/ITO. (a) Schematic of a parallel RC system based on dynamic memristors. Each memristor RC unit has a different mask sequence. The output is a linear combination of all reservoir states. This parallel RC system is achieved by testing individual memristors over multiple cycles. The output vector is a linear combination of values from virtual nodes, and weights (W_out) can be trained using linear regression. (b) 16 encoding state diagrams of memristors, reflecting previous temporal information through different photocurrents. (c) Prediction results from the parallel RC system based on memristors. The purple line represents actual outputs, while the pink line represents predicted outputs of the RC system. The mask length is 9, with 25 masks. The training set: test set ratio is 7 : 3. (d) Confusion matrix of prediction results versus correct outputs from the RC system based on Au/C₂₇H₃₀O₁₅/FeO_x/ITO memristors, achieving an accuracy of 94.88%. The color bar indicates the normalized probability of each predicted result under the correct output.