A High Current Density Direct‐Current Generator Based on a Moving van der Waals Schottky Diode

Abstract

nanogenerator can only output alternating current and the output current density is quite small (0.01-0.1 A m −2 ), [5] which limits its widespread applications. [6] Recently, the vertical movement between the metal and semiconducting polymer has been demonstrated to output intermittent current peaks with low current density (2.7-62.4 µA cm −2 ), [7] where the metal contacts with polymer periodically. On the other hand, the microscale direct current generator based on sliding between metal tip and semiconductor has been demonstrated, [8] where the mechanism was ascribed to the triboelectric effect. However, the mechanism of triboelectric effect is confusing, [9] as the fundamental physical mechanism of the charge transfer process during friction is not solved. [6,10] Herein, we have demonstrated a macroscale direct-current generator through a moving van der Waals Schottky diode by dynamically moving graphene or metal film over Si or GaAs substrates. The mechanism of the moving Schottky diode generator is based on the built-in electric field separation of the diffusing carriers emitted by the appearance and disappearance of the depletion layer in moving Schottky diode. The working lifetime and flexibility can be properly improved by choosing graphene as the metal material, which is outstanding not only because of its high conductive but also the high mechanical physical properties. [11,12] Actually, static graphene/semiconductor van der Waals heterostructure-based solar cells, [13] self-driven photodetectors, [14] and water flow nanogenerator [15] have been proposed. Compared with metal, graphene film has the unique advantage of high flexibility and durability, which promises the graphene film/ silicon moving Schottky diode generator working well after 10 000 runs back and forth. The persistent direct-current generating ability firmly demonstrates that the physical mechanism of the moving Schottky diode generator is not caused by the triboelectricity. Instead, we uniquely propose that the dynamic disappearance and establishment of Schottky junction during the movement between graphene/metal and semiconductors is the origin of the direct current output. The proposed mechanism is self-consistent and can well explain the systematic experiments presented herein. This moving Schottky diode direct-current generator can light up a blue light-emitting diode (LED) and a flexible graphene wristband is demonstrated for the first time. Under the guidance of the mechanism, we achieved a currentdensity output up of ≈40 A m −2 through minimizing the contact Traditionally, Schottky diodes are used statically in the electronic information industry while dynamic or moving Schottky diode-based applications are rarely explored. Herein, a novel Schottky diode named "moving Schottky diode generator" is designed, which can convert mechanical energy into electrical energy by means of lateral movement between the graphene/metal film and semiconductor. The mechanism is based on the built-in electric field separation of the diffusing carr...

Tribo‐Tunneling DC Generator with Carbon Aerogel/Silicon Multi‐Nanocontacts

“…[19] Here, we shall also see that pulsing DC signal is generated but with similar output magnitude under linear reciprocal rubbing (Figure 2e,f). [7] The short-circuit J value is four times higher than the maximum dielectric AC that polymer-based TENG can possibly achieve in atmosphere (≈0.05 A m −2 ). The power output is maximized when R ≈ 146 kΩ, which approximates the internal resistance r of the system.…”

“…[1] The performance of TENGs is optimal only at high frequency due to the dielectric displacement current mechanism, while the environmental mechanical sources usually have frequencies lower than 10 Hz. [3,[5][6][7][8][9][10] The tribo-tunneling transport tip-enhanced current generation, as reported by Liu et al [3,6] using conductive-atomic force microscope (C-AFM), show that the tribo-tunneling current density ( J) output can be boosted by the nano-sized contact (tip radius R ≈ 30 nm) up to 10 6 A m −2 due to the enhanced electronic excitation and strong localized electric field E. It has been reported that a micro-tip (tip radius R ≈ 30 µm) sliding system produces a current density of 35 A m −2 while larger tip radius (R ≈ 100-300 µm) yields a current density of 10 A m −2 in the test probe sliding system. [3,[5][6][7][8][9][10] The tribo-tunneling transport tip-enhanced current generation, as reported by Liu et al [3,6] using conductive-atomic force microscope (C-AFM), show that the tribo-tunneling current density ( J) output can be boosted by the nano-sized contact (tip radius R ≈ 30 nm) up to 10 6 A m −2 due to the enhanced electronic excitation and strong localized electric field E. It has been reported that a micro-tip (tip radius R ≈ 30 µm) sliding system produces a current density of 35 A m −2 while larger tip radius (R ≈ 100-300 µm) yields a current density of 10 A m −2 in the test probe sliding system.…”

Tribovoltaic Effect on Metal–Semiconductor Interface for Direct‐Current Low‐Impedance Triboelectric Nanogenerators

“…sliding metal-insulator-semiconductor (MIS) structure, [14][15][16][17] the moving Schottky diode based on metal-semiconductor (MS) structure, [18][19][20] the triboelectric cell based on PN junction structure, [21][22][23] and other moving heterojunction nanogenerator. [24] Thundat and Liu et al realized an ultrahigh current density MIS nanogenerator due to quantum mechanical tunneling of the ultrathin natural oxide layer.…”

“…[14][15][16] Lin et al designed a moving Schottky diode generator with high current density output which is based on the built-in electric field separation. [18] Zhang and Xu et al reported a direct-current triboelectric cell by sliding PN junction and indicated that its mechanism may be the formation of electron-hole pairs. [22] It is true that these novel generators with continuous, high-density, and direct-current output characteristics have shown great interest and potential, but the power generation mechanisms of them remain to be extensively studied.…”

Theoretical study of superlubric nanogenerators with superb performances

“…However, low electric current densities and short product lifespans of current nanogenerators have blocked real applications of nanogenerators explored so far 3,6,18 .…”