A Guide for Cross-Linking Modulation: The Record Rectifying Ratio of Hydrogel-Based Ultra Flexible Ionic Diodes

Abstract

This study focuses on the effect of cross-linking mechanisms in the development of hydrogel-based flexible ionic diodes (HBIDs) with desirable features for ionic devices. The research explores one p-type hydrogel and a series of n-type hydrogels with varying cross-linking ratios, investigating their ion-conducting properties, morphological and electronic structures, as well as the performance of flexible HBIDs constructed using these hydrogels. The results indicate that the cross-linking ratio significantly influences ionic conductivity, bulk resistance, and capacitance. Additionally, the HBIDs' ability to maintain their electrical performance under repeated mechanical bending is studied concerning the cross-linking ratio. Notably, the HBID with the highest cross-linking ratio (HG/12) exhibits relatively higher current densities (up to 8.9 mA cm−2) and considerably higher rectification ratios (up to 1269). Even after 500 cycles of deformation, the HG/12 diode maintained a rectification ratio of 987, demonstrating its excellent performance and durability.