Regensburg 2013 – scientific programme
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DS: Fachverband Dünne Schichten
DS 10: Organic Electronics and Photovoltaics I (jointly with CPP, HL, O)
DS 10.3: Talk
Monday, March 11, 2013, 17:45–18:00, H32
Full electronic structure across a polymer heterojunction solar cell: interface dipoles and influence of light — •Johannes Frisch1, Patrick Amsalem1, Jens Niederhausen1, Marcel Schubert2, Eduard Preis3, Antje Vollmer4, Jürgen P. Rabe1, Ullrich Scherf3, Dieter Neher2, and Norbert Koch1 — 1Humboldt-Universität zu Berlin, Germany — 2Universität Potsdam, Germany — 3Bergische Universität Wuppertal, Germany — 4Helmholtz-Zentrum Berlin für Materialien und Energie - Speicherring BESSY II, Berlin, Germany
Controversial discussions concern the dependence of open circuit voltage on the energy offset between the highest occupied molecular orbital level of the donor material and the lowest unoccupied molecular orbital level of the acceptor material in organic photovoltaic cells. Therefore, we investigate the energy level alignment in two bi-layer OPVCs comprising the donor poly(3-hexylthiophene) (P3HT) and the acceptors 1-(3-methoxycarbonyl)propyl-1-phenyl[6.6]C61 (PCBM) and poly(9,9'dialklylfluorene-alt- 4,7-bis(2,5-thiendiyl)-2,1,3-benzothiadiazole) (PFTBTT). Ultraviolet photoelectron spectroscopy revealed that notable interface dipoles occur at all interfaces across the OPVC structures for both material combinations. Particularly, the effective electrode work function (after contact formation with the organic material) differs significantly from those of the pristine materials. In addition, we find that negative charges are collected at the metal clusters (that exist in the early stage of cathode formation) due to exciton dissociation at the heterojunction.