Ionic Diffusion‐Driven Ionovoltaic Transducer for Probing Ion‐Molecular Interactions at Solid–Liquid Interface

Abstract

Ion-solid surface interactions are one of the fundamental principles in liquid-interfacing devices ranging from various electrochemical systems to electrolyte-driven energy conversion devices. The interplays between these two phases, especially containing charge carriers in the solid layer, work as a pivotal role in the operation of these devices, but corresponding details of those effects remain as unrevealed issues in academic fields. Herein, an ion-charge carrier interaction at an electrolyte-semiconductor interface is interrogated with an ion-dynamics-induced (ionovoltaic) energy transducer, controlled by interfacial self-assembled molecules. An electricity generating mechanism from interfacial ionic diffusion is elucidated in terms of the ion-charge carrier interaction, originated from a dipole potential effect of the self-assembled molecular layer (SAM). In addition, this effect is found to be modulated via chemical functionalization of the interfacial molecular layer and transition metal ion complexation therein. With the aiding of surface analytic techniques and a liquid-interfacing Hall measurement, electrical behaviors of the device depending on the magnitude of the ion-ligand complexation are interrogated, thereby demonstrating the ion-charge carrier interplays spanning at electrolyte-SAM-semiconductor interface. Hence, this system can be applied to study molecular interactions, including chemical and physical influences, occurring at the solid-liquid interfacial region.

Ionovoltaic electricity generation over graphene-nanoplatelets: protein-nanofibril hybrid materials

“…A possible explanation of the generation of electricity during water evaporation is related to the ionovoltaic effect, 12,15,16 where ionic movement is coupled with movement of charge carriers in the conductive (GNP) phase of the device, as shown in Fig. 5a and S12 ‡.…”

“…As ionic movement in the aqueous phase combined with interfacial ion–charge carrier interactions lead to movement of charge carriers in the conductive phase (providing a voltage) this type of process may appropriately be labeled as an ionovoltaic process. 8,12,15–17 It should be noted that similar processes have been labeled as hydrovoltaics in many recent publications, even though ionic species often are involved in the operating mechanisms. Regardless of the choosen label, this approach has recently received much interest; for example, by employing carbonaceous materials such as carbon nanotubes and graphene as electrically conductive phase.…”

High-Precision Stretchable Ionic Temperature Sensor Passivated with a Liquid Metal/Block Copolymer Multilayer Film

“…Over the past decade, ion-based stretchable electronics have received intensive attention due to the potential uses in deformable physical sensors to monitor strain, 1,2 touch, 3,4 pressure, 5,6 temperature, 7,8 and biological chemical changes. 9 Delicate synaptic control is expected to be achieved by the ionovoltaic signal generation 10 and the organic electrochemical transistors (OECTs). 11−13 However, the moisture dependence of the ion properties is a challenging drawback of the ion gelbased sensors.…”

“…Over the past decade, ion-based stretchable electronics have received intensive attention due to the potential uses in deformable physical sensors to monitor strain, , touch, , pressure, , temperature, , and biological chemical changes . Delicate synaptic control is expected to be achieved by the ionovoltaic signal generation and the organic electrochemical transistors (OECTs). − However, the moisture dependence of the ion properties is a challenging drawback of the ion gel-based sensors. , The impedance of the ion gel can shift down under high relative humidity (RH) or under a water environment. This humidity dependence results from the intrinsic property changes such as the bulk conductivity (σ) and permittivity (ε). , Although Kim et al recently demonstrated that maintaining the ion gel layer in a water-saturated state can effectively eliminate the moisture dependence of the electrochemical performance of ion gel, complete water passivation is conventional and immediately applicable to a wide range of stretchable devices.…”

Moisture-Induced Ionovoltaic Electricity Generation by Manipulating Organic–Inorganic Hybrid Halide Perovskites

“…Initial studies on the water motion active transducer using a dielectric layer and a hydrophobic layer show that the dielectric constant of the dielectric layer determines the amount of energy harvested . The ion–solid interactions and the solid–liquid interfacial potentials determine the output voltage driven by the macroscopic water motion. − The primary mechanism of this process is dependent on the reversible hydration and dehydration of the materials. The preformed ionizable groups with gradient distribution release out hydrated ions when exposed to moisture.…”