Tunable piezoelectric nanogenerators using flexoelectricity of well-ordered hollow 2D MoS2 shells arrays for energy harvesting

Piezoelectric two-dimensional (2D) transition-metal dichalcogenides such as molybdenum disulfide (MoS2) have recently attracted significant attention owing to their applicability for fabrication of flexible power generators. In this study, novel piezoelectric nanogenerators (PNGs) consisting of 2D piezoelectric MoS2 shells are fabricated where an Al2O3 thin layer deposited on the surface of polystyrene (PS) beads is used to avoid collapse of the spherical MoS2 shells under the high growth temperature. In addition, the MoS2 shell size is controlled by adjusting the PS bead size and the effects of the MoS2 shell size on power generation characteristics are investigated. Our PNG based on the piezoelectric MoS2 shells produces a peak output voltage of approximately 1.2 V at a pressure of 4.2 kPa. The minimum pressure for power generation by tapping is 0.3 kPa. This novel method is very promising for development of the next-generation PNGs based on 2D semiconductor piezoelectric materials.