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DS: Fachverband Dünne Schichten
DS 55: Organic Thin Films III
DS 55.2: Vortrag
Freitag, 11. März 2016, 09:45–10:00, H8
Correlating the donor/acceptor interface energetics with electronic dynamics in organic bilayer solar cells — •Michael Brendel1, Essraa Ahmed2, Iulia Minda2, Heinrich Schwoerer2, and Jens Pflaum1,3 — 1Exp. Physics VI, Julius-Maximilians-University Würzburg, D-97074 Würzburg — 2Laser Research Institute, Stellenbosch University, ZA-7602 Matieland — 3Bavarian Center for Applied Energy Research (ZAE Bayern), D-97074 Würzburg
The crucial functional building block of any state of the art organic solar cell is the donor/acceptor (D/A) heterojunction. At this interface, the energetic offset of the frontier orbitals between donor and acceptor drives the dissociation of excitons into free charge carriers.
In this contribution we systematically tune the D/A interface energetics of bilayer cells by successive fluorination of the donor material zinc phthalocyanine, FnZnPc (n = 0, 4, 8, 16). As evinced by ultraviolet photoelectron spectroscopy, upon fluorination energy levels of the donor are shifted towards lower energies with respect to the acceptor C60. [1] The static picture of interface energetics is complemented by correlation with the excitonic and electronic dynamics accessed via ultrafast transient absorption spectroscopy. Exciton separation at the respective FnZnPc/C60 interface takes place on fs-time scale, increasing in speed with increasing energetic offset at the D/A interface. After initial exciton dissociation, recombination dynamics of electrons in C60 remain almost unaffected by the D/A interface energetics on a ps-time scale. Financial support from SOLTECH and the DAAD.
[1] M. Brendel et al., Adv. Funct. Mater., 2015, 25, 1565.