Multiwavelength-Responsive Plasticity in a Bias-Free Perovskite Synaptic Device for Neuromorphic Vision

Low-power and color-sensitive neuromorphic vision systems are critical to the next generation of intelligent devices. Here, we report a coral-inspired, lead-free synaptic device based on Cs₃Bi₂Br₉ perovskite nanocrystals prepared by centrifugal casting into a porous thin film. The device exhibits wavelength-dependent plasticity under 405, 520, and 635 nm illumination without an external bias. By modulating the light wavelength and intensity, short-term and long-term synaptic plasticity are achieved to mimic excitatory, inhibitory, and saturating biological responses. Structural and spectroscopic analyses reveal that bromine vacancies play a key role in the dynamic modulation of carrier transport and plasticity evolution. The efficient preprocessing of RGB visual information significantly enhances recognition accuracy in artificial neural network devices. This wavelength-specific modulation of synaptic plasticity, a novel approach for color image preprocessing and recognition, is very promising for the advancement of neuromorphic systems.