Berlin 2008 – scientific programme
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SYSA: Symposium Tayloring Organic Interfaces: Molecular Structures and Applications
SYSA 5: Poster Session SYSA
SYSA 5.27: Poster
Tuesday, February 26, 2008, 14:30–20:00, Poster A
Vacuum deposited films of dicyanovinylene-capped oligothiophenes for use in organic solar cells — •Marieta Levichkova1, David Wynands1, Moritz Riede1, Martin Pfeiffer2, Eduard Brier3, Egon Reinold3, Peter Bäuerle3, and Karl Leo1 — 1Institut für Angewandte Photophysik, TU Dresden, 01062 Dresden — 2Heliatek GmbH, 01187 Dresden — 3Institut für Organische Chemie II und Neue Materialien, Universität Ulm, 89081 Ulm
Solar cells based on oligothiophene derivatives comprising electron-accepting dicyanovinyl groups have shown high power efficiencies (up to 3.4%). Here, we study the effect of substrate temperature on the morphology and photopysical properties of DCV6T (α,ω-bis-(dicyanovenylen)-sexithiophene) films with the aim to optimize the active layer structure. The films are prepared by vapor deposition on quartz substrates covered with amorphous hole transport layer. During the evaporation of DCV6T, the substrates are kept at constant temperatures between 20∘C and 100∘C. AFM images show increased grain size and surface roughness of the samples grown at higher Tsub. The alteration of surface topography is accompanied by an enhanced and red-shifted absorption which we attribute to a more ordered molecular arrangement leading to a co-planarization of the thiophene rings within the oligomers. Also, for the samples grown at Tsub ≥ 80∘C, the overlap between absorption and luminescence increases which suggests an increase in exciton diffusion length. Finally, we will discuss the effect of the various DCV6T morphologies on the performance of solar cells.