Characterization of α-phenyl-4′-(diphenylamino)stilbene single crystal and its anisotropic conductivity

Abstract Presently, organic-semiconductor electronics suffer from low performance owing to their amorphous nature. Improving their crystallinity, and thus the charge transport properties is a crucial endeavor. Accordingly, this study aims to elucidate the conductivity mechanism of a novel triphenylamine-derivative single crystal. We successfully synthesized an α-phenyl-4′-(diphenylamino)stilbene (TPA) single crystal via a solution method employing the solubility and supersolubility curves of TPA in the tetrahydrofuran (THF) solvent. Its crystal structure was determined via single-crystal X-ray diffraction (SCXRD), which revealed that the obtained single crystal contains not only TPA but also THF. The molecular ratio of TPA to THF was found to be 2:0.74. We further analyzed the hole transport property in three directions of the single crystal, and the anisotropic conductivity was observed. Based on the results of the observed molecular packing and charge transport property, we confirm that the observed anisotropic conductivity is determined based on the orientation of the triphenylamine unit in each direction of the TPA single crystal. Overall, the findings can help in guiding the design of high-mobility organic semiconductors for realizing more effective organic electronic devices.