Tribovoltaic Nanogenerators Based on MXene–Silicon Heterojunctions for Highly Stable Self‐Powered Speed, Displacement, Tension, Oscillation Angle, and Vibration Sensors

Abstract

Tribovoltaic nanogenerators (TVNGs), an emerging high‐entropy energy harvesting technique, present great features such as low matching resistance, high current density, and continuous output performance. Here, an MXene layer and a semiconducting silicon wafer are assembled into a tribovoltaic nanogenerator (named MS‐TVNG). The output peak current of the MS‐TVNG reaches up to 22 µA for a P‐type (0.1–0.5 Ω cm) silicon wafer under a normal force of 4.56 N and a sliding speed of 2 m s−1. Owing to the unique metal characteristics of the MXene layer, the performance is superior to those previously reported TVNGs using traditional metals. The layered structure of MXene endows the real‐time MS‐TVNG with outstanding wear‐resistance and stable output properties. The performance of the MS‐TVNG can be tuned by the doping type and concentration of the silicon wafer, as well as by the pressure and the relative sliding speed between two friction surfaces. The MS‐TVNG has proven to be a solid foundation for high‐performance self‐powered speed sensors and has excellent potentials for applications in displacement, tension, oscillation angle, and vibration detection.

Simultaneously Enhancing Direct‐Current Density and Lifetime of Tribovotaic Nanogenerator via Interface Lubrication

“…The GWS-TVNG generates DC signal based on the tribovoltaic effect, when Cu-G film, water-based GO solution, and silicon wafer contact, carrier equilibrium will be re-established at the interface due to different work functions of the materials. During sliding friction, new chemical bonds are formed at the interface, which release energy, called "bindington", [26,30] and the "bindington" excites electron-hole pairs at the sliding interface. The electron-hole pairs are then separated and expelled out of the Schottky junction under the action of the built-in electric field, resulting in a continuous DC signal.…”

“…[ 29 ] TVNG based on MXene‐silicon heterojunctions was proposed, which can reach a high output peak current of 22 µA, as well as the enhanced lifetime of over 1800 cycles. [ 30 ] In addition, macro‐superlubric TVNG can operate stably for nearly 10 000 cycles. [ 31 ] By adding organic lubricating oil, the TVNG can increase its lifetime to 20 000 cycles, but the addition of lubricating oil cannot achieve high output and even slightly decrease the output.…”

Friction-Dominated Carrier Excitation and Transport Mechanism for GaN-Based Direct-Current Triboelectric Nanogenerators

“…At present, the SDC-TENG has made a series of structures: stainless steel–silicon, graphene–silicon, platinum–silicon, and other combinations have shown excellent performances. − The SDC-TENG based on black phosphorus/AlN/Si heterojunction achieves an open-circuit voltage of 6.1 V . By controlling the friction between the nanoprobe of an atomic force microscope and the semiconductor surface, ,,− current densities as high as 2 × 10 8 A/m 2 can be achieved for SDC-TENGs .…”

A humidity-enhanced silicon-based semiconductor tribovoltaic direct-current nanogenerator

“…On the other hand, the tribovoltaic effect which transitions the study of the TENG from insulators to semiconductor materials could utilize the interface friction on the semiconductor interface to generate direct current. [39][40][41][42][43][44][45][46][47][48] Different from the traditional TENG where the transferred charge is related to the surface electrostatic charges of the insulating materials, the transferred charge of the tribovoltaic effect is related to the carrier excited by friction, 49 which would not dissipate in high-humidity environments. Therefore, the semiconductor TENG based on the tribovoltaic effect is expected to achieve a performance breakthrough in highhumidity environments.…”