Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 18: Organic semiconductors I
CPP 18.2: Vortrag
Mittwoch, 28. März 2012, 09:45–10:00, C 130
Influence of aggregation on the performance of all-polymer solar cells containing low-bandgap naphthalenediimide-copolymers. — •Marcel Schubert1, Daniel Dolfen2, Johannes Frisch3, Steffen Roland1, Robert Steyrleuthner1, Burkhard Stiller1, Zhihua Chen4, Ullrich Scherf2, Norbert Koch3, Antonio Facchetti4, and Dieter Neher1 — 1University of Potsdam, Germany — 2University of Wuppertal, Germany — 3Humboldt University Berlin, Germany — 4Polyera Corporation, USA
Naphthalene-diimide (NDI) or perylene-diimide (PDI) containing copolymers are promising alternatives for replacing fullerenes as the electron-accepting phase in organic solar cells. So far, the power conversion efficiencies (PCEs) of all-polymer solar cells comprising NDI/PDI-based copolymers and regio-regular poly(3-hexylthiophene) (P3HT) remained below 1%. It was proposed that the NDI/PDI-copolymers exhibit a strong tendency to aggregate, which promotes long range phase separation and unfavourable nanomorphologies.
Our studies of the optical properties of such copolymers in different solvents reveal a strong tendency to pre-aggregate. This pre-aggregation could be fully suppressed by adding suitable high boiling point solvents. Solar cells prepared from these solvent mixtures showed PCEs of up to 1.4% and high fill factors of up to 70%, which are among the highest reported values for polymer-polymer blends. Finally, SNOM and AFM measurements in combination with optical absorption studies reveal a surprising anticorrelation between the degree of chain aggregation and the photovoltaic device performance.