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

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.