Nanoampere‐Level Piezoelectric Energy Harvesting Performance of Lithography‐Free Centimeter‐Scale MoS₂ Monolayer Film Generators

Abstract

2D transition‐metal dichalcogenides have been reported to possess piezoelectricity due to their lack of inversion symmetry; thus, they are potentially applicable as electromechanical energy harvesters. Herein, the authors propose a lithography‐free piezoelectric energy harvester composed of centimeter‐scale MoS2 monolayer films with an interdigitated electrode pattern that is enabled only by the large scale of the film. High‐quality large‐scale synthesis of the monolayer films is conducted by low‐pressure chemical vapor deposition with the assistance of an unprecedented Na2S promoter. The extra sulfur supplied by Na2S critically passivates the sulfur vacancies. The energy harvester having a large active area of ≈18.3 mm2 demonstrates an unexpectedly high piezoelectric energy harvesting performance of ≈400.4 mV and ≈40.7 nA under a bending strain of 0.57%, with the careful adjustment of side electrodes along the zigzag atomic arrays in the two dominant domain structure. Nanoampere‐level harvesting has not yet been reported with any 2D material‐based harvester.

Ultrahigh photoresponse in strain- and domain-engineered large-scale MoS2 monolayer films

“…S1 of the ESI,† the successful formation of a large-scale monolayer was enabled by this Na 2 S growth promotor, which also passivated sulfur vacancies. As reported previously by our group, 26 the growth mechanism of MoS 2 under the presence of Na 2 S likely differs from the typical reaction between MoO 3 and S precursors. Because Na evaporates earlier according to the Born–Haber cycle, gas-phase Na reacts with MoO 3 powder to form NaMoO 3− x .…”

“…Prior to the in situ straining process, large-scale monolayer MoS 2 films were synthesized on a sapphire substrate via low-pressure chemical vapor deposition (LPCVD) with the assistance of a unique Na 2 S growth promotor, as reported in our previous study. 26 A photograph of the synthesized large-scale MoS 2 monolayer film with dimensions of ∼15 × 15 mm is shown in the inset of Fig. 1a.…”

“…The preferred growth is the result of a minimal lattice mismatch with the c -plane (0001) sapphire substrate, whereas growth on the Si substrate usually leads to the random growth of triangular domains. 26,29,30 The electrodes were directionally adjusted according to the domain structure of the monolayer film in three different ways, as illustrated in Fig. 1c.…”

Roadmap on energy harvesting materials

“…As another recent example of inorganic nanostructures, two-dimensional dichalcogenide materials ranging in thickness from a single atomic layer up to a few nanometers have been introduced as potential piezoelectric nanogenerators. The energy-harvesting outcomes of a large-area monolayer MoS 2 film reached ∼0.4 V and ∼40.7 nA with optimal domain configurations relative to the position of the interdigitated electrodes [129]. Applications using inorganic nanostructures have been extended to self-powered wearable systems with diverse functionalities, which may also be suitable for artificial intelligence and machine learning systems interfacing with human motions and activities [130,131].…”

Anomalous Dynamics of Defect-Assisted Phonon Recycling in Few-Layer Mo0.5W0.5S2

“…Atomically thin 2D transition metal dichalcogenides (TMDCs) have been widely studied owing to their excellent optical and electronic properties, , such as direct band gap, large exciton binding energy at room temperature, and spin and valley physics, − compared with conventional semiconductor materials. They provide opportunities for the design of new photoelectric detectors, energy storage, , flexible devices, , and photocatalysts . Many strategies, such as electromagnetic field, , mechanical strain, , chemical modulation, , high pressure , and others, have been proposed to regulate the properties of 2D materials.…”