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.