Single Crystal Growth of Cyclopenta-Fused Polycyclic Aromatic Hydrocarbon by the Naphthalene Flux Method: 2D Ambipolar Charge Transport Properties and NIR Absorption

Compared to simple p- and n-type organic field-effect
transistors,
it is very difficult to achieve high performance in ambipolar transistors
because both HOMO–HOMO and LUMO–LUMO interactions in
the crystal must be large and multidimensional. We have experimentally
and theoretically investigated three types of cyclopenta-fused polycyclic
aromatic hydrocarbon molecules with narrow HOMO–LUMO gaps and
found that one of them is a two-dimensional ambipolar material. Although
the crystal structures of these molecules have not been reported due
to their low solubility in common organic solvents, we have succeeded
in revealing their crystal structures using the naphthalene flux method.
1,2,6,7-Tetraphenyldicyclopenta[cd,jk]pyrene crystals have a brick-work
structure, which is expected to be promising for two-dimensional charge
transport. Theoretical calculations using the obtained molecular arrangement
suggested that there are two-dimensional interactions for both HOMO–HOMO
and LUMO–LUMO. Experimental investigation confirmed ambipolar
operation in a single-crystal FET. In addition, near-infrared absorption
due to intermolecular charge-transfer interactions was observed despite
the single-component nature of the material, suggesting its potential
for use in photoelectric conversion devices.