| Abstract
| - Discotic liquid crystals emerge as very attractive materials for organic-based (opto)electronicsas they allow efficient charge and energy transport along self-organized molecular columns. Here, angle-resolved photoelectron spectroscopy (ARUPS) is used to investigate the electronic structure andsupramolecular organization of the discotic molecule, hexakis(hexylthio)diquinoxalino[2,3-a:2‘,3‘-c]phenazine,deposited on graphite. The ARUPS data reveal significant changes in the electronic properties when goingfrom disordered to columnar phases, the main feature being a decrease in ionization potential by 1.8 eVfollowing the appearance of new electronic states at low binding energy. This evolution is rationalized byquantum-chemical calculations performed on model stacks containing from two to six molecules, whichillustrate the formation of a quasi-band structure with Bloch-like orbitals delocalized over several moleculesin the column. The ARUPS data also point to an energy dispersion of the upper π-bands in the columnsby some 1.1 eV, therefore highlighting the strongly delocalized nature of the π-electrons along the discoticstacks.
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