Investigation on two triphenylene based electron transport materials

Promoting electron mobility is the key to designing high performance electron transport materials (ETMs). Formation of intermolecular interaction can be helpful to enhance their electron mobilities as a result of more ordered molecular stacking. Here, to reveal the inherent influence of intermolecular π-π stacking on the electron mobilities, we designed two ETMs, namely, 2,4-diphenyl-6-[3-(2-triphenylenyl)phenyl]-1,3,5-triazine (TPTRZ) and 2,4-diphenyl-6-[4′-(2-triphenylenyl)[1,1′-biphenyl]-3-yl]-1,3,5-triazine (TPPTRZ). Thermal, photophysical and electrochemical measurement results indicate they are good ETM candidates. Additionally, TPTRZ and TPPTRZ exhibit high electron mobilities of 3.60×10⁻⁵ and 3.58×10⁻⁵ cm² V⁻¹ s⁻¹, respectively, at an electric field of 7×10⁵ V cm⁻¹. By taking X-ray single crystal structure, theoretical calculation and time of flight (TOF) results into consideration, it is revealed that strong intermolecular π-π stacking induced by planar triphenylene and triphenyltriazine units renders TPTRZ and TPPTRZ small energetic and positional disorder parameters, and results in their high electron mobilities thereby. By further enhancing intermolecular π-π stacking, ETMs with even higher electron mobilities can thus be anticipated.