Regensburg 2016 – scientific programme
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DS: Fachverband Dünne Schichten
DS 42: Organic Electronics and Photovoltaics II
(Joint session of CPP, DS, HL and O, organized by CPP)
DS 42.5: Talk
Thursday, March 10, 2016, 10:45–11:00, H40
PBDT[2F]T: Insight into the Secrets of a Wide Band-Gap Polymer with 7% Power Conversion Efficiency — •Julien Gorenflot1,2, Andreas Paulke3, Fortunato Piersimoni3, Federico Cruciani2, Dieter Neher3, Pierre M Beaujuge2, and Frédéric Laquai2 — 1Max Planck Institut für Polymerforschung, Mainz, Germany — 2King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia — 3Universität Potsdam, Potsdam, Germany
PBDT[2F]T :fullerene blends exhibit performance up to 75% higher than the reference P3HT:PCBM solar cells [1]. Using femto- to microsecond transient absorption, we investigate the origin of those outstanding properties. We find that geminate recombination losses of photogenerated charge carriers are nearly absent in PBDT[2F]T:fullerene blends. Field-dependent measurement as well as morphological and energy levels characterization reveal efficient and field-independent charge generation, enabling excellent short-circuit current and fill factor. Strikingly, this outstanding generation is achieved in spite of a rather low offset between the polymer's excitons and the blend's charge transfer state energy levels, which allows for an open circuit voltage as high as 0.9 V. Replacing the fluorine substituents by hydrogen in those polymers results in only moderate performances, thus highlighting the importance of molecular design. This is discussed in terms of energy levels and blends morphology.
[1] J. Wolf et al., Chem. Mater. 27, 2015