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...

SummaryThe static PN junction is the foundation of integrated circuits. Herein, we pioneer a high current density generation by mechanically moving N-type semiconductor over P-type semiconductor, named as the dynamic PN junction. The establishment and destruction of the depletion layer causes the redistribution and rebounding of diffusing carriers by the built-in field, similar to a capacitive charge/discharge process of PN junction capacitance during the movement. Through inserting dielectric layer at the interface of the dynamic PN junction, output voltage can be improved and designed numerically according to the energy level difference between the valence band of semiconductor and conduction band of dielectric layer. Especially, the dynamic MoS2/AlN/Si generator with open-circuit voltage of 5.1 V, short-circuit current density of 112.0 A/m2, power density of 130.0 W/m2, and power-conversion efficiency of 32.5% has been achieved, which can light up light-emitting diode timely and directly. This generator can continuously work for 1 h, demonstrating its great potential applications.

A light-and mechanical-energy co-harvesting generator based on a dynamic metal/perovskite Schottky junction with output current density of 41.1 A/m 2 is reported, which reveals a nonlinear photo-enhanced effect related to the nonlinear interaction between the mechanical energy-induced bound back carriers and photo-generated carriers in dynamic metal/perovskite Schottky junction. Without obvious degradation when being bent 120 , the flexible Al/perovskite generator is promising for utilization as a flexible and portable power source.

Nowadays, many different kinds of novel generators have been introduced to convert nature power into electrical power, such as mechanical energy, [1,2] hydraulic energy, [3] solar energy, [4,5] thermal energy, [6] etc. These generators all possess an electric field to output power, however, the large

Static heterojunction-based electronic devices have been widely applied because carrier dynamic processes between semiconductors can be designed through band gap engineering. Herein, we demonstrate a tunable direct-current generator based on the dynamic heterojunction, whose mechanism is based on breaking the symmetry of drift and diffusion currents and rebounding hot carrier transport in dynamic heterojunctions. Furthermore, the output voltage can be delicately adjusted and enhanced with the interface energy level engineering of inserting dielectric layers. Under the ultrahigh interface electric field, hot electrons will still transfer across the interface through the tunneling and hopping effect. In particular, the intrinsic anisotropy of black phosphorus arising from the lattice structure produces extraordinary electronic, transport, and mechanical properties exploited in our dynamic heterojunction generator. Herein, the voltage of 6.1 V, current density of 124.0 A/m2, power density of 201.0 W/m2, and energy-conversion efficiency of 31.4% have been achieved based on the dynamic black phosphorus/AlN/Si heterojunction, which can be used to directly and synchronously light up light-emitting diodes. This direct-current generator has the potential to convert ubiquitous mechanical energy into electric energy and is a promising candidate for novel portable and miniaturized power sources in the in situ energy acquisition field.