Application of ion-in-conjugation molecules in resistive memories and gas sensors: The role of conjugation

Abstract

Ion-in-conjugation (IIC) materials are emerging as an important class of organic electronic materials with wide applications in energy storage, resistive memories and gas sensors. Many IIC materials were designed and investigated, however the role of conjugation in IIC materials’ performance is yet investigated. Here we designed two molecules obtained by condensation of 4-butylaniline and oxocarbon acid. Squaric acid derivatives squaraine named SA-Bu and a croconamide named CA-Bu which only differ in their oxocarbon cores. While employing SA-Bu and CA-Bu as resistive memory and gas sensory materials, SA-Bu has attained promising performance in ternary memory and detection of NO2 as low as 10 parts-per-billion whereas CA-Bu show mainly binary memory behavior and negligible NO2 response. Theoretical calculations reveal that conjugation of CA-Bu was distorted by the increased steric hindrance, frustrating the charge transport and suppressing the conductivity. Our work demonstrates that the conjugation plays a crucial role in ion-in-materials promoting ternary RRAM devices and high-performance gas sensors manufacture.