Preparation of Highly-Ordered Tetrabenzorporphyrin Films Controlled by Supramolecular Assemblies and Precursor Approach

Abstract

The control of the orientation and packing structures of small organic semiconductor molecules is the important issue for the improvement of charge carrier mobilities of organic field effect transistors. Tetrabenzoporphyrin (BP) is one of the promising p-type organic semiconductors but solubility in organic solvents is very low. We have developed a precursor approach, where a spun-cast film of soluble precursor, tetra-bicyclo[2.2.2]octadiene-fused porphyrin (CP), was heated to obtain BP crystalline film by in-situ retro-Diels–Alder reaction. However, the obtained BP film is a polycrystalline film and the field-effect transistors (FETs) hole mobilities were 10-1~10-2 cm2V-1s-1[1]. Recently, we reported the effect of alkyl substituents at 5,15-positions of BP for the control of the molecular arrangement. The best performance of OFET hole mobility of 5,15-disubstituted BP was 4.1 cm2V-1s-1 [2, 3].A supramolecular strategy has attracted attentions as the effective method for the control of molecular arrangement in films. We applied the combination of supramolecular assembling method and the precursor approach to prepare well-ordered BP films. 5,15-Bis(p-dodecylamidephenyl)-CP was deposited on the substrate by drop-casting, spin-coating or dip-coating method, followed by the heating to 200 ºC for 10 min to give the corresponding 5,15-bis(p-dodecylamidephenyl)-BP films. The film morphologies of the BP were compared with 5,15-bis(p-dodecyloxyphenyl)-BP, which doesn’t include amide moieties for hydrogen-bonding, using UV-vis absorption spectroscopy, atomic force microscopy (AFM), X-ray diffraction (XRD) analysis, and p-polarized multiple-angle incidence resolution spectrometry (p-MAIRS) to clarify the effect of amide groups. OFET performance of the BPs will be also discussed to clarify the effect of intermolecular hydrogen bonding interaction.