The surface potential of a thin film of 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi), which is a typical molecule used in organic light-emitting diodes, linearly increases with the film thickness due to the spontaneous orientation of the permanent dipole of TPBi. Recently, we demonstrated that TPBi can be used as an electret for vibrational energy harvesting (VEH). This means that TPBi can be regarded as a self-assembled electret (SAE). The advantage of an SAE-based VEH is that no charging process is needed during device fabrication. We believe that the application of SAEs will lead to the dissemination of VEH technology.