Self‐Stratified Trilayer Architecture Enables Multifunctional Flexible Organic Photonic Synaptic Transistors With Ultra‐Low Energy Consumption

Blending organic semiconductors with insulating polymers can significantly enhance the electronic and mechanical performance, as well as stability of organic field‐effect transistors. However, devices fabricated based on such blends typically exhibit a weak response to light stimulation due to the intrinsically low light absorption of insulators, which presents considerable challenges in their application for photonic synaptic transistors. In this work, a self‐stratified trilayer architecture is spontaneously formed from a one‐step blend of DPP‐DTT and PMMA. The top and bottom semiconducting sublayers optimize the exciton generation and charge transport, respectively, while the PMMA‐rich interlayer provides outstanding flexibility and stability. This unique structure endows the device with a high on/off ratio (>10 6 ), pronounced photosensitivity (2.61 × 10 4 ), robust environmental stability, and excellent mechanical compliance. The devices faithfully emulate key synaptic functions and further enable diverse neuromorphic demonstrations, including optical logic operations, Morse code decoding, and handwritten digit recognition, with an ultra‐low electrical energy consumption down to 2.7 aJ per synaptic event. This work establishes a scalable and cost‐effective route toward large‐area fabrication of flexible organic synaptic transistors, unlocking broad opportunities in wearable electronics, neuromorphic bioelectronic interfaces, and health monitoring.