Dresden 2017 – wissenschaftliches Programm
CPP 33.6: Vortrag
Mittwoch, 22. März 2017, 10:45–11:00, POT 81
Photovoltaic Performance of Organic Photodiodes Based on Homochiral Squaraine Compounds — •Manuela Schiek1, Matthias Schulz2, Majvor Mack1, Oliver Kolloge1, Dominik Höweling1, and Arne Lützen2 — 1University of Oldenburg — 2University of Bonn
The substitution pattern of non-toxic and environmentally stable dihydroxy-anilino squaraines  is modified with natural chiral functional groups such as a prolinol derivative. These natural compounds are available in their enantiomerically pure forms making costly separation of racemic product mixtures obsolete. Strong circular dichroism is measured in spin-casted thin films proving homo-chiral aggregation. Blended with a fullerene acceptor, these squaraines perform as light harvesting compound in a conventional bulk heterojunction photodiode. The performance depends on the blend ratio of squaraine and fullerene as well as on active layer thickness. In all cases, the devices suffer from low fill factors. Thinner layers lead to S-shaped current voltage characteristics around Voc. In addition, a thin active layer device with a high fullerene percentage is impacted by a photoshunt under illuminated reverse current conditions . This becomes visible in reverse voltage biased EQE measurements showing a spectrally dependent deformation of the photocurrent response with the EQE exceeding 100% in the spectral response regime of the fullerene.  Schiek et al. Langmuir 32 (2016) 8533.  Tress et al. Phys. Stat. Solidi RRL 7 (2013) 401.