Kinetic swelling-driven PTG interlayers for enhanced crystallinity and charge transport in polymer OECTs

Abstract

Organic semiconductors (OSCs) are essential for future flexible electronics due to their unique flexibility and tunable molecular structure. However, controlling substrate surface properties to enhance OSC crystallinity through low-temperature solution processes remains challenging. In this study, a polyvinyl alcohol (PVA)-based supporting interlayer modified with glutaraldehyde (GA) and Triton-X is developed to enhance OSC crystallization and charge transport characteristics. GA crosslinking reduces hydroxyl (-OH) groups that can trap charges, while Triton-X micelles create a semi-porous structure, facilitating polymer solution absorption and crystal growth. The modified PVA-based interlayer significantly improves the crystallinity of poly(3-hexylthiophene) (P3HT) and poly[2,5-bis(3-tetradecythiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT), as confirmed by X-ray diffraction analysis. Under optimal wetting conditions, the coherence length of P3HT and PBTTT crystals increases by 148% and 83%, respectively, compared to pristine films. These enhancements lead to a 7.2 times increase in the product of mobility and volumetric capacitance (mu C*) of P3HT-based organic electrochemical transistors (OECTs), reaching 123.13 F cm-1 V-1 s-1. Additionally, the neuromorphic performance of P3HT OECTs supported on the modified interlayer is attributed to superior synaptic behavior, achieving higher paired-pulse facilitation (about 180%), long-term potentiation (LTP), and long-term depression (LTD) characteristics compared to pristine devices. These results pave the way for high-performance OSC-based neuromorphic applications.