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.