Methoxy-substituted naphthothiophenes – Single molecules' vs. condensed phase properties and prospects for organic electronics applications

A series of tricyclic naphthothiophenes – photocyclization products (8-methoxynaphtho[1,2-b]thiophene; 6,7-dimethoxynaphtho[1,2-b]thiophene; 8-methoxynaphtho[2,1-b]thiophene) have been studied. HOMO and LUMO levels, as well as a gap between them was accessed by cyclic voltammetry and optical spectroscopy. Double potential step chronoamperometry showed that the former naphthothiophene exhibits slower current decay than the other substances. Charge carrier mobility measured by the CELIV technique was estimated to be of the order of 10⁻⁴ cm²V⁻¹s⁻¹ for 0.2 µm films and approaches 10⁻¹ cm²V⁻¹s⁻¹. for the 5 µm film of 8-methoxynaphtho[1,2-b]thiophene. It is believed the high mobility is associated with the ordering of the high conductivity axis of the microcrystals in the layers.