Spontaneous orientation polarization driven by designing molecular asymmetry

Abstract Organic polar small molecules exhibit spontaneous orientation polarization (SOP) in vacuum-deposited amorphous films. This phenomenon arises because of the asymmetric molecular interactions at the interface between the film surface and vacuum during the deposition process. Here, we investigate the impact of functional groups on the SOP of bent-shaped polar molecules. The results demonstrate that the differences in polarizability between the head and tail functional groups in polar molecules drive the orientation polarization in the films. Enhancing the SOP involves the introduction of two functional groups with distinct polarizabilities in the head and tail groups to promote asymmetric interactions. The developed polar molecule, incorporating bulky alkyl and sulfonyl groups, exhibits a high surface potential growth rate of +321 mV nm −1 in the SOP film. These findings enable the precise control of the molecular orientation in amorphous films and the development of highly polarized electret materials without charging processes.