Aggregation modulation of conjugated polymers by carbon dots for optoelectronic synaptic transistors and artificial visual recognition

Developing low-power and highly stable optoelectronic synaptic devices is essential for emulating visual neuromorphic functions. Herein, hydrophobic nitrogen/sulfur-doped carbon quantum dots (N/S-CDs) synthesized via a one-step hydrothermal method effectively promote the enhanced aggregation of conjugated-polymer poly [2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole-alt-5,5(2,5-di(thien-2-yl) thieno [3,2-b] thiophene)]. Meanwhile, benefiting from the abundant surface functional groups and defect states of N/S-CDs, the resulting organic optoelectronic synaptic transistor (OOST) exhibits diverse synaptic behaviors, including linear multibit storage capability and wavelength-dependent synaptic plasticity, together with a retention time exceeding 1000 s and a 1.3 × 106Ion/Ioff ratio. Neuromorphic functionalities such as learning and memorizing QR code patterns, decoding encrypted optical signals, and recognizing handwritten digits with 92.58% accuracy are successfully emulated. This work highlights the critical roles of energy-level alignment and defect-mediated charge trapping in N/S-CDs, offering a promising strategy for designing simple, efficient, and stable nonvolatile OOSTs for future artificial visual systems.