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.