Artificial synapses have gained considerable attention in modeling artificial visual systems. Facile and efficient p-n heterojunction, acting as the essential component, plays a critical role in configuration optimization and processing capabilities. Herein, we introduced a novel charge-transfer cocrystal that consisted of 5,8-dihydroindolo[2,3-c]carbazole (DDCB) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) via solution-process, which demonstrated good crystallinity and typical n-type charge transport characteristics. To realize good charge storage ability, crystalline p-n heterojunctions with a phase-separated heterostructure were one-step prepared by drop-casting TIPS-pentacene and DDCB/TCNQ solutions onto the substrate. The as-prepared artificial synaptic devices exhibited remarkable paired-pulse facilitation (PPF), spike-duration dependent plasticity, spike-intensity dependent plasticity, and learning-experience behaviors similar to those of biological synapses in response to light pulses. Furthermore, based on the light potentiation and electrical depression modulation properties of these synaptic devices, we constructed artificial neural networks for image recognition, achieving a validation accuracy of over 97% on the modified national institute of standards and technology (MNIST) dataset. This work provides a new simple approach in establishing p-n heterojunction based artificial synapses for applications in light information processing, artificial vision, and memory simulation.
Organic semiconductor (OSC) films fabricated by meniscus-guided coating (MGC) methods are suitable for cost-effective and flexible electronics. However, achieving crystalline thin films by MGC methods is still challenging because the nucleation and crystal growth processes are influenced by the intertwined interactions among solvent evaporation, stochastic nucleation, and the fluid flow instabilities. Herein, a novel flexible fountain pen with active ink supply is designed and used to print OSCs. This direct-write method allows the flexible pen tip to contact the substrate, maintaining a robust meniscus by eliminating the gap found in conventional MGCs. An in situ optical microscopy observation system shows that the precursor film plays a critical role on the crystallization and the formation of coffee rings and dendrites. The computational fluid dynamics simulations demonstrate that the microstructure of the pen promotes extensional flows, facilitating mass transport and crystal alignment. Highly-aligned ribbon-shaped crystals of a small organic molecule (TIPS-pentacene), as well as a semiconducting polymer (N2200) with highly-ordered orientations, have been successfully printed by the flexible fountain pen. Organic field-effect transistors based on the flexible pen printed OSCs exhibit high performances and strong anisotropic mobility. In addition, the flexible fountain pen is expandable for printing multiple lines or large-area films.
危险品化学品经营许可证（带存储）