Flat-on ambipolar triphenylamine/C60 nano-stacks formed from the self-organization of a pyramid-sphere-shaped amphiphile

Abstract

A giant amphiphile, which is constructed with an amorphous nano-pyramid (triphenylamine, TPA) and a crystalline nano-sphere (C₆₀), was synthesized. Structural characterization indicates that this pyramid-sphere-shaped amphiphile (TPA–C₆₀) forms a solvent-induced ordered phase, in which the two constituent units self-assemble into alternating stacks of two-dimensional (2D) TPA and C₆₀ nano-sheets. Due to the complexity of the molecular structure and the amorphous nature of the nano-pyramid, phase formation was driven by intermolecular C₆₀–C₆₀ interactions and the ordered phase could not be reformed from the TPA–C₆₀ melt. Oriented crystal arrays of TPA–C₆₀, which contain flat-on TPA/C₆₀ nano-stacks, can be obtained via a PDMS-assisted crystallization (PAC) technique. The flat-on dual-channel supramolecular structure of TPA–C₆₀ delivered ambipolar and balanced charge-transport characteristics with an average μ_e of 2.11 × 10⁻⁴ cm² V⁻¹ s⁻¹ and μ_h of 3.37 × 10⁻⁴ cm² V⁻¹ s⁻¹. The anisotropic charge-transport ability of the pyramid-sphere-shaped amphiphile was further understood based on the lattice structure and the lattice orientation of TPA–C₆₀ revealed from electron diffraction analyses.