Low-Energy Vertical Organic Synaptic Transistors Enabled by Siloxane Crosslinking-Induced Edge-On Molecular Ordering

The von Neumann bottleneck has driven the development of low-power neuromorphic devices such as vertical organic synaptic transistors (VOSTs), which offer ultrashort charge transport pathways and high integration density. However, their performance is still limited by poor molecular ordering and the difficulty in achieving effective gate-controlled modulation. Here, a siloxane crosslinking strategy is proposed by incorporating 1,6-bis(trichlorosilyl)hexane (C6Si) into poly(3-hexylthiophene) (P3HT) to form a dense cross-linked network, enabling improved molecular ordering, backbone planarity, and interfacial stability. As a result, a pronounced edge-on molecular orientation of 93.00% was achieved, establishing efficient vertical charge transport pathways. The ion gel-gated VOSTs exhibited excellent electrical performance at an ultralow operation voltage (-0.5 V), including high on/off current ratio (I_on/I_off) (9.48 × 10⁴), low subthreshold swing (SS) (111 mV dec^-1), and the minimum synaptic-event energy consumption at low level (∼50 aJ), along with rich synaptic plasticity. Ex-situ neural network simulations demonstrate over 91% accuracy in MNIST handwritten digit recognition. Meanwhile, the device arrays enable high-contrast image reconstruction and visual memory functions, providing an effective molecular design strategy for the development of low-cost, scalable neuromorphic computing devices.