Point‐Defect‐Passivated MoS2 Nanosheet‐Based High Performance Piezoelectric Nanogenerator

In this work, a sulfur (S) vacancy passivated monolayer MoS2 piezoelectric nanogenerator (PNG) is demonstrated, and its properties before and after S treatment are compared to investigate the effect of passivating S vacancy. The S vacancies are effectively passivated by using the S treatment process on the pristine MoS2 surface. The S vacancy site has a tendency to covalently bond with S functional groups; therefore, by capturing free electrons, a S atom will form a chemisorbed bond with the S vacancy site of MoS2. S treatment reduces the charge‐carrier density of the monolayer MoS2 surface, thus the screening effect of piezoelectric polarization charges by free carrier is significantly prevented. As a result, the output peak current and voltage of the S‐treated monolayer MoS2 nanosheet PNG are increased by more than 3 times (100 pA) and 2 times (22 mV), respectively. Further, the S treatment increases the maximum power by almost 10 times. The results suggest that S treatment can reduce free‐charge carrier by sulfur S passivation and efficiently prevent the screening effect. Thus, the piezoelectric output peaks of current, voltage, and maximum power are dramatically increased, as compared with the pristine MoS2. Piezoelectricity of sulfur vacancy passivated MoS2 nanosheets is much higher than that of pristine MoS2 nanosheets. Sulfur vacancies can be filled through a sulfur treatment and the resulting output power of the device generates a 10‐times higher power. This result offers a new approach to realize a MoS2 nanosheet‐based high‐performance piezoelectric nanogenerator for self‐powered wearable electronics.