Berlin 2018 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
CPP: Fachverband Chemische Physik und Polymerphysik
CPP 2: Electrical, Dielectrical and Optical Properties of Thin Films I
CPP 2.5: Vortrag
Montag, 12. März 2018, 10:30–10:45, C 230
Investigating optical excitations in push-pull molecular J-aggregates by TDDFT first-principles simulations — •Michele Guerrini1,2, Arrigo Calzolari2, and Stefano Corni2,3 — 1Dept. of Physics, Information and Mathematics , University of Modena and Reggio Emilia, Italy — 2CNR Nano Modena, Italy — 3Dept. of Chemical Sciences, University of Padova, Italy
J-aggregates are a class of molecular crystals which show interesting optical properties such as an intense and narrow red-shifted absorption peak (aka J-band) with respect to the monomer units they are composed of. In this work we investigated the electronical optical properties of a J-aggregate molecular crystal made of ordered arrangements of organic push-pull chromophores. By using a TDDFT first-principles approach, we assessed the role of molecular packings in the formation of the enhanced and red-shifted J-band and the major effects of confinement in the optical absorption when moving from bulk to low-dimensional crystal structures. In particular, we simulated the optical absorption of different configurations (i.e. monomer, dimers, extended polymer chain and monolayer sheet) obtained from the bulk crystal. By analyzing the induced charge density associated to the J-band, we concluded that this characteristic peak is mostly associated to a longitudinal excitation that is delocalized along linear chains within the bulk crystal and its red-shift is explained in terms of couplings between transition densities along these chains, as well as changes in single particle excitations, that lowers the total excitation energy.