High work function silver nanowire electrodes via ligand exchange reaction for stretchable organic thin-film transistors

Abstract

Silver nanowires (AgNWs), as promising conductor materials, have found their application in various stretchable electronics. However, the mismatch between the work function of AgNWs electrodes and energy level of semiconductors limits the obtaining of high-performance devices, especially in stretchable p-type organic thin film transistors (OTFTs) where the resulting severe injection barrier significantly lowers the overall performance of the devices. In this study, we prepared stretchable AgNWs electrodes with high work function that closely matched the highest occupied molecular orbital (HOMO) of the p-type polymer semiconductor poly(indacenodithiophene-co-benzothiadiazole) (IDT-BT) via a ligand exchange reaction with fluorinated molecules and post-treatment-free fabrication. In comparison to the commercial polyvinylpyrrolidone (PVP) stabilized AgNWs, electrodes based on ligand-exchanged AgNWs exhibited higher work function over 5 eV, closer to the HOMO of IDT-BT. As a result, IDT-BT-based p-type OTFTs fabricated using ligand-exchanged AgNWs electrodes achieved a reduced threshold voltage and improved carrier transport property, with a hole mobility of 0.4 cm² V⁻¹ s⁻¹. Moreover, the ligand exchange on the surface of AgNWs caused no deterioration of the deformability of the resulting devices, largely retaining the original mobility after being stretched by 30% strain. These results demonstrate the effectiveness of the work function tuning via the ligand-exchange strategy in the processing of AgNWs electrodes for enhancing the performance of stretchable electronics.