Excitonics of Squaraine Dunes Frank Balzer 1 , Marvin F. Schumacher 2 , Arne Lützen 2 , Manuela Schiek 3 1 University of Southern Denmark, Centre for Photonics Engineering, Denmark 2 Kekulé Insitute of Organic Chemistry and Biochemistry, Germany 3 LIOS &; ZONA, Johannes Kepler University, Austria
Squaraine thin films are gaining significant attention in the field of optoelectronics due to their unique, anisotropic optical properties. They have a high photostability and exhibit strong absorption in the visible and near-infrared region, making them ideal for applications in photovoltaics and photodetectors. The prototypical squaraine SQIB, Fig. 1(a) , condenses into two different polymorphs, both with different optical, electronic, and mechanical properties. The formation of periodic dunes can be induced during crystallization, Fig. 1(b,c) . For the orthorhombic polymorph [1] , the real parts of the dielectric tensor become strongly negative [2] , allowing field enhancement at sharp objects such as the tips of the dunes or at narrow cracks. Raman microscopy together with polarized absorption spectro- microscopy and nanomechanical characterization paint a full picture of the excitonic coupling within the dunes.
Fig. 1. (a) SQIB. (b) AFM image of monoclinic SQIB thin film dunes. A Fourier-transform, inset in (b), together with a cross section (c) along the green line demonstrates their spatial periodicity. References 1. F. Balzer, T. Breuer, G. Witte, M. Schiek, Template and Temperature-Controlled Polymorph Formation in Squaraine Thin Films, Langmuir 38 (2022) 9266. 2. S. Funke, M. Duwe, F. Balzer, P.H. Thiesen, K. Hingerl, M. Schiek, Determining the Dielectric Tensor of Microtextured Organic Thin Films by Imaging Mueller Matrix Ellipsometry, J. Phys. Chem. Lett. 12 (2021) 3053.
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© The Author(s), 2023
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