TY - JOUR A1 - Kowarik, Stefan A1 - Pithan, L. A1 - Nabok, D. A1 - Cocchi, C. A1 - Beyer, P. A1 - Duva, G. A1 - Simbrunner, J. A1 - Rawle, J. A1 - Nicklin, C. A1 - Schäfer, P. A1 - Draxl, C. A1 - Schreiber, F. T1 - Molecular structure of the substrate-induced thin-film phase of tetracene N2 - We present a combined experimental and theoretical study to solve the unit-cell and molecular arrangement of the tetracene thin film (TF) phase. TF phases, also known as substrate induced phases (SIP), are polymorphs that exist at interfaces and decisively impact the functionality of organic thin films, e.g., in a transistor channel, but also change the optical spectra due to the different molecular packing. As SIPs only exist in textured ultrathin films, their structure determination remains challenging compared to bulk materials. Here, we use grazing incidence Xray diffraction and atomistic simulations to extract the TF unit-cell parameters of tetracene together with the atomic positions within the unit-cell. KW - X-ray DIFFRACTION KW - Tetracene KW - Semiconductor KW - Optoelectronics KW - Molecule PY - 2018 U6 - https://doi.org/10.1063/1.5043379 VL - 149 IS - 14 SP - 144701-1 EP - 144701-5 PB - AIP Publishing AN - OPUS4-46399 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Duva, G. A1 - Pithan, L. A1 - Zeiser, C. A1 - Reisz, B. A1 - Dieterle, J. A1 - Hofferberth, B. A1 - Beyer, P. A1 - Bogula, L. A1 - Opitz, A. A1 - Kowarik, Stefan A1 - Hinderhofer, A. A1 - Gerlach, A. A1 - Schreiber, F. T1 - Thin-Film Texture and Optical Properties of Donor/Acceptor Complexes. Diindenoperylene/F6TCNNQ vs Alpha-Sexithiophene/ F6TCNNQ N2 - In this work, two novel donor/acceptor (D/A) complexes, namely, diindenoperylene (DIP)/1,3,4,5,7,8-hexafluoro-tetracyanonaphthoquinodimethane (F6TCNNQ) and alpha-sexithiophene (6T)/F6TCNNQ, are studied. The D/A complexes segregate in form of π−π stacked D/A cocrystals and can be observed by X-ray scattering. The different conformational degrees of freedom of the donor molecules, respectively, seem to affect the thin-film crystalline texture and composition of the D/A mixtures significantly. In equimolar mixtures, for DIP/F6TCNNQ, the crystallites are mostly uniaxially oriented and homogeneous, whereas for 6T/F6TCNNQ, a mostly 3D (isotropic) orientation of the crystallites and coexistence of domains of pristine compounds and D/A complex, respectively, are observed. Using optical absorption spectroscopy, we observe for each of the two mixed systems a set of new, strong transitions located in the near-IR range below the gap of the pristine compounds: such transitions are related to charge-transfer (CT) interactions between donor and acceptor. The optical anisotropy of domains of the D/A complexes with associated new electronic states is studied by ellipsometry. We infer that the CT-related transition dipole moment is perpendicular to the respective π-conjugated planes in the D/A complex. KW - Optical properties KW - Molecular semiconductor KW - X-ray diffraction PY - 2018 U6 - https://doi.org/10.1021/acs.jpcc.8b03744 SP - 18705 EP - 18714 PB - ACS AN - OPUS4-46400 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -