Photoactive Nanocomposite Dielectric-Driven Low-Power All-Optical Organic Synaptic Transistors

Artificial optical synapses featuring low-energy consumption, high speed, and noise tolerance are critical for visual neuromorphic electronics. Most existing devices rely on complex multilayer structures or require high supply voltages to induce carrier tunneling effects. Therefore, we propose a photoactive nanocomposite dielectric (PND) layer, thereby enabling an embedded-layer-free, low-voltage, low-power optical organic synaptic transistor (OST) capable of all-optical, optical-electrical, and all-electrical modulation. We achieve this by functionalizing titanium dioxide nanoparticles (TiO₂ NPs) with nitrile butadiene rubber to fabricate a photo-curable, patternable PND layer. Under electrical and optical stimulation, the PND-based OST exhibits outstanding synaptic characteristics, including spike-width-dependent plasticity, spike-number-dependent plasticity, spike-rate-dependent plasticity, as well as long-term potentiation and long-term depression. Notably, this device achieves a low-energy consumption of 10.09 fJ at V_D = -1 mV. We further propose a new energy assessment framework to quantify the energy consumption of synaptic weight modulation in neural network computations, providing a more practical evaluation metric. In a neuromorphic image recognition, integrating optically tunable synaptic weights into a deep neural network achieves a recognition accuracy of 92.7% under high-noise conditions through all-optical modulation. Overall, PND structure not only simplifies device fabrication but also offers a promising solution for developing efficient, low-power neuromorphic electronic devices.