First-principles studies on organic electronic materials

Abstract

Abstract. The elucidation of physical properties of organic materials is important for further optimization of related electronic and optoelectronic devices. Here we review briefly various first-principles computational tools for the modeling of these materials by investigating key structural, electronic, and chemical properties of prototype organic semiconductors. In particular, we discuss the site-selectivity for band formation in pentacene and rubrene, hydrogenation and transformations of metal-free phthalocyanines, and the bonding topology in a hybrid organic-inorganic system. PACS

Intermolecular bridges and carrier traps in defective C60crystals

“…25 In agreement with previous studies, 25 we found that the energy of the (5,8) configuration is significantly lower (by 1.2 eV) than that of (4,9). While (5,8) is nonmagnetic, (4,9) bears a magnetic moment of 1.9 μ B . The migration of a vacancy between neighboring (5,8) configurations on a C 60 molecule involves multistep transformations that include (4,9) structures as intermediate geometry.…”

“…The removal of a C atom from a C 60 molecule triggers significant relaxation of the surrounding atoms, so that eventually two of the three C dangling bonds are eliminated through the formation of a new pentagon or square. The reconstructed structures can be called (5,8) and (4,9), respectively. 25 In agreement with previous studies, 25 we found that the energy of the (5,8) configuration is significantly lower (by 1.2 eV) than that of (4,9).…”

“…The reconstructed structures can be called (5,8) and (4,9), respectively. 25 In agreement with previous studies, 25 we found that the energy of the (5,8) configuration is significantly lower (by 1.2 eV) than that of (4,9). While (5,8) is nonmagnetic, (4,9) bears a magnetic moment of 1.9 μ B .…”

“…While (5,8) is nonmagnetic, (4,9) bears a magnetic moment of 1.9 μ B . The migration of a vacancy between neighboring (5,8) configurations on a C 60 molecule involves multistep transformations that include (4,9) structures as intermediate geometry. Based on the large calculated activation energy of 2.1 eV, we infer that hopping of vacancies on the fullerene molecule requires annealing at high temperatures.…”

“…Similar to the case of other organic semiconductors, [6][7][8][9] however, the performance of C 60based devices depends on the presence of imperfections, either in the form of chemical impurities, 10 or as native defects. These imperfections may degrade transport properties of electronic materials through the formation of levels in the energy-band gap of the host system or levels close to the valence-and conduction-band edges.…”