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.
