Attachable piezoelectric nanogenerators using collision-induced strain of vertically grown hollow MoS₂ nanoflakes

Piezoelectric materials convert external mechanical force into electrical energy, due to the breaking of the centrosymmetry of the atomic structure. Piezoelectricity-based nano-generators (PNGs) based on two-dimensional transition metal dichalcogenides (TMDs) can generate electrical energy stably by the piezoelectric effect at their nanoscale thickness. However, the commercialization of TMD-based PNGs is limited by their poor piezoelectric performance and microscale energy harvesting. Here, we present the first centimeter-scale PNGs based on molybdenum disulfide (MoS₂) nanosheets with vertically grown hollow MoS₂ nanoflakes (v-MoS₂ NFs) obtained by chemical vapor deposition for energy harvesting from human motions. The collision of v-MoS₂ NFs with a preferred odd-atomic-layer number and their 2H antiparallel phase leads to efficient electrical energy generation during the bending movement. Further, basal MoS₂ films with v-MoS₂ NFs are transferred onto flexible substrates via conventional polymer-assisted methods for the fabrication of attachable and wearable piezoelectric power generators.