Berlin 2018 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 115: Molecular films: Photovoltaics, electronics and morphology (joint session O/CPP)

O 115.1: Vortrag

Freitag, 16. März 2018, 10:30–10:45, MA 144

Excitonic states in films of 1,3-diphenylisobenzofuran — •Janek Rieger, Daniel Niesner, and Thomas Fauster — Lehrstuhl für Festkörperphysik, University of Erlangen-Nürnberg, Staudtstr. 7, D-91058 Erlangen, Germany

Films of 1,3-diphenylisobenzofuran (DPIBF) show singlet fission (SF), a mechanism for multi-exciton generation that might be used to enhance the efficiency of organic photovoltaics [1]. The yield of singlet fission depends strongly on the structural polymorph of the film [2]. We use ultraviolet photoelectron spectroscopy, monochromatic two-photon photoelectron spectroscopy, photoluminescence (PL) spectroscopy and time-resolved PL to investigate the occupied molecular orbitals and excitonic behavior in different polymorphs of DPIBF on Cu(111). Preparations under ultra-high vacuum conditions provided well-defined samples, on which in-situ measurements were carried out. In disordered films an excimer trapping state with a lifetime of 50 ns was found with an energy ∼0.5 eV below the first excited singlet state S₁. For ordered films additional three vibrational progressions were found, which can be attributed to the S₁ excitons of two different polymorphs with energies of 2.62 eV and 2.66 eV and an emissive triplet pair species with an energy of 2.72 eV. The latter decays with two time constants in the subnanosecond regime. A relative PL yield <0.12 was determined for the ordered films, which points towards a highly SF active film.
M. C. Hanna, and A. J. Nozik, J. Appl. Phys. 100, 074510 (2006).
J. L. Ryerson et al., J. Phys. Chem. C 118, 12121-12132 (2014).