UV-responsive phototransistor for hierarchical synaptic plasticity

Emulating biological synaptic plasticity is essential for advancing artificial intelligence. However, in most existing synaptic phototransistors to date, both electrical and optical stimuli induce weight modulation within a comparable dynamic range, limiting plasticity tunability and richness. Here, we report a synaptic phototransistor that enables distinct weight modulation in response to electrical and optical inputs, achieving hierarchical, multi-scale plasticity with concurrent visible-light emission for direct display. The device integrates a long-afterglow material that converts transient ultraviolet (UV) excitation into persistent visible emission, serving as a temporally extended, memory-like optical stimulus. Compared to direct electrical gating, this delayed optical activation of the optoelectronic channel induces weight modulation on a significantly longer timescale, enabling hierarchical plasticity and cascade interactions between optical and electrical pathways. The dual-output architecture allows simultaneous optical visualization and electrical signal processing, effectively integrating optical perception with insensor computation. Leveraging this design, we demonstrate a UV-resolvable neural network capable of direct image display and achieving a recognition accuracy of 95.03% for handwritten digits. This work establishes a new paradigm for multimodal neuromorphic systems by seamlessly integrating sensing, display, and computation within a unified in-sensor architecture.