Elastomer‐Assisted Segregation Growth of Large‐Scale Stretchable Organic Crystalline Films for Flexible Photosynapses

Organic semiconducting single crystals are ideal candidates for flexible artificial photonic synapses (APSs) owing to their superior photoelectric properties. However, large-area high-quality organic single crystals are rarely obtained on the elastomer substrates commonly used in flexible electronics. Herein, inspired by soil salinization, we developed a segregation strategy to in situ grow large-area organic single crystals on elastomer substrates via a simple air-water interface drop-casting method. Solvent-evaporation-driven phase separation in organic semiconductor-elastomer blends promotes molecular migration, leading to a precipitation behaviour that enables the fabrication of centimetre-scale organic single-crystal nanosheet film directly on elastomer surfaces. Planar APS devices based on a mode molecule, 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT), demonstrate exceptional synaptic functionality, including 171% paired-pulse facilitation (PPF) and ultralow power consumption of 0.15 fJ per synaptic event. Leveraging a synergistic stress-dispersion mechanism involving nanosheet sliding and elastic substrate deformation, these devices retain synaptic performance under 15% tensile strain and after 60 days of ambient storage without encapsulation. The results shed light on the large-area fabrication of organic single crystals on elastomer toward high-performance flexible neuromorphic electronics.