Hybrid piezoelectric-triboelectric nanogenerators for flexible electronics: mechanisms, applications, and future prospects

The ever-increasing demand for sustainable and portable power sources has led to the development of hybrid piezoelectric-triboelectric nanogenerators (HPTENGs) for energy harvesting. HPTENGs are hybrid-based devices that utilize the principles and benefits offered by piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs) in an efficient manner to harness mechanical energy. This review article attempts to give overview of HPTENGs, their working principles, focusing on the fundamental principles underlying charge transfer. In addition to this, it will describe the combined effects offered by piezoelectric and triboelectric effects in HPTENGs. The underlying principles by which HPTENGs enhance energy harvesting performance are discussed, which are supported by relevant experimental and theoretical evidence. Parameters which contribute to higher efficiency in HPTENGs, including material properties, surface patterns, designs, interfaces, and environmental effects are also discussed. On the other hand, applications of HPTENGs regarding energy harvesting, flexible wearable electronics, self-powered sensing, and environmental sensing are also presented. It will be summed up by stating the hurdles faced by HPTENGs and their possible contributions to next-generation flexible and sustainable devices.