Characterization of electronic structure of low-dimensional organic molecular crystals

Most charge-transfer ion-radical salts have dimerized stacks of donor and/or acceptor molecules. The optical properties of such molecular crystals are usually described by the model of independent dimers where electronic correlations are treated in the Hubbard fashion and electron—molecular vibration (EMV) coupling is taken into account. In order to investigate the influence of inter-dimer interactions, the complex conductivity for several arrays of larger linear clusters is calculated for different values of the ratio between inter- and intra-dimer transfer integrals. The role of interactions between orthogonal dimers in bidimensional organic semiconductors (κ-phase) is also evaluated. Positions of charge-transfer electronic excitation bands and vibrational bands are discussed as a function of the size and dimensionality of the molecular cluster.