POLAR MOLECULES BASED ELECTRET FOR VIBRATIONAL ENERGY GENERATOR

Abstract

Electret-based vibrational energy generator (VEGs) have attracted attention because electrical power can be generated from ambient vibrations. VEGs typically have a capacitor structure in which an electret and an air gap are sandwiched between the top and bottom electrodes. Electret is a dielectric material with a quasi-permanent electrical charge or dipole polarization. The output power of VEGs depends on the surface charge density (σ) of electret, and therefore the σ must be enhanced. Corona charging is one of the most widely used technique to charge dielectric materials, that is, to make electret, however, this charging process limits productivity of the device. Thus the simplification of fabrication process is highly required. In this study, we applied evaporated film composed of polar molecules, such as tris-(8-hydroxyquinolinato) aluminium (Alq3) and 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi), as electret. It has been reported that surface potential of these films linearly increases with the film thickness without any charging process. This is because these are polar molecule and spontaneously order perpendicular to the substrate. By taking advantage of this film, we prepared polar moleculesbased VEGs. During electrode vibration, AC current clearly appeared. This result suggests that VEG which does not require any charging process is realized by utilizing polar molecules as electret. Finally, we thank Profs. Hiroyuki Fujita, Yuji Suzuki, and Hiroshi Toshiyoshi, for their helpful discussion. This research was supported by JST, PRESTO Grant Number JPMJPR17R6, Japan.