Stability improvement against light irradiation by dye doping in self-assembled electret-based vibrational energy harvester

Abstract

Self-assembled electrets (SAEs), in which polar molecules such as Alq3 and TPBi are spontaneously ordered by vapor deposition, are promising materials for vibrational energy generators (VEGs). SAEs can simplify fabrication process of VEGs because the charging process, e.g. corona charging, is not required; however, SAEs are sensitive for light irradiation because charge carriers are generated by exciton dissociation, leading to compensation of polarization charge on the SAE surface. In order to restrict charge generation, in this study, the dye molecule is doped into SAE having a wider optical gap than that of dye molecule. In the doped SAE, exciton energy is transferred to the dye, resulting in exciton quenching. In this work, we doped Alq$_{3}(2.4$ vol%) to TPBi which has a wide optical gap, and stability of VEG composed of the doped film was evaluated during light irradiation. We demonstrate that the retention time of 50% loss in the device was 2.6 times longer than that of neat TPBi-based VEG. This result suggests that the application of doped SAE is quite useful to realize long-lived SAE-based VEG.