Electronic View of Triboelectric Nanogenerator for Energy Harvesting: Mechanisms and Applications

Abstract

The world is facing an ongoing energy crisis, which is caused by constantly declined fossil fuel capacity and induced environmental pollutions in both atmosphere and ocean. Despite the construction of solar panels for harvesting solar and wind energy, the overall production still dissatisfies the requirements for loading enormous rising technologies and diverse devices. Although enormous research has been dedicated to investigate novel energy harvesting strategies, most of the inventions cost astonishingly high prices or require complicated equipment to achieve utilizable output, which blocks further practical developments. Hydropower is a renewable, sustainable energy source contained in moving water and continuously renewed by the sun. Owing to the huge quantity, low cost, and broad applications, hydropower becomes a superior and desirable candidate for the manufacture of portable energy supplies. To date, the typical method of harvesting kinetic energy contained in water movements is well known as the electromagnetic generator (EMG). However, such a strategy usually requires the relatively high speed of the water movement, which induces significant obstacles to further development. Nanogenerator was invented for converting nanoscale mechanical energy into electrical energy via electrical polarization, which was unprecedentedly proposed by Wang and co-workers. When bending a piezoelectric zinc oxide nanowire, charges on the surface moved and rearranged, creating a strain field. Nowadays, the studies of flexible nanogenerators have been extensively and comprehensively advanced. These works indicate that the integration of flexibility and stretchability of the nanogenerator device is the predominant factor determining the performances and durability of practical applications, such as low-power portable electronics and self-powered sensors. This new concept of nanogenerator relying on piezoelectrification and triboelectrification can constantly harvest mechanical energy contained in an ambient environment, thereby constituting a new type of self-powered sustainable energy supply. A large amount of nanogenerators has so far been specifically designed and fabricated on account of complex circumstances and triggers. The piezoelectric nanogenerator is typically applied in the system with asymmetric pressures; the strain can introduce the electrical polarization and charge Q. Lu, M. Sun, Prof. B. Huang Department of Applied Biology and Chemical Technology The Hong Kong Polytechnic University Hung Hom, Kowloon, Hong Kong SAR, China E-mail: [email protected] Prof. Z. L. Wang Beijing Institute of Nanoenergy and Nanosystems Chinese Academy of Sciences Beijing 100083, China E-mail: [email protected] Prof. Z. L. Wang School of Materials Science and Engineering Georgia Institute of Technology Atlanta, GA 30332, USA