Systematic study of the electronic states in electron-doped polyacenes

High-quality polycrystalline polyacenes (PLAs) of anthracene (AN), tetracene (TN), and pentacene (PN) doped with potassium in the 1:1 and 1:2 stoichiometries are prepared and their physical properties are systematically studied by magnetic measurements. The magnetic susceptibilities as a function of temperature for K_x(PLAs) are interpreted in the framework of a band-filling model. Clear evidence for the occurrence of charge transfer from K to the organic semiconductors is provided. K₁(AN) prepared by a solid-state diffusion process exhibits a pronounced magnetic hump at 140 K, which is associated with antiferromagnetic interactions ascribed to the on-site Coulomb repulsion in a Mott insulating state, whereas both K₁(TN) and K₁(PN) show a conventional Curie-Weiss behavior at low temperatures. We successfully demonstrate the tuning of the electronic states of PLA-type semiconductors in bulk. Comments are given about the possibility of metallic states in potassium-doped PLAs, which have recently been reported for other polycyclic aromatic hydrocarbons. We prepared K-intercalated polyacenes (PLAs) by using an improved methodology. The magnetic susceptibilities as a function of temperature for K_x(PLAs) are described in the framework of a band-filling model. We successfully tuned the electronic states of the fused-ring semiconductors in bulk.