Regensburg 2016 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 30: Poster: Organic Electronics and Photovoltaics
CPP 30.25: Poster
Dienstag, 8. März 2016, 18:15–21:00, Poster B2
Effect of the donor orientation on the VOC losses in small molecule organic bilayer solar cells. — •Steffen Roland1, Niva Ran2, Thuc-Quyen Nguyen2, and Dieter Neher1 — 1University of Potsdam, Institute of Physics and Astronomie, Potsdam, Germany — 2University of California Santa Barbara, Center for Advanced Organic Photovoltaics, USA
Bilayer solar cells based on the donor molecule p-SIDT(FBTTh2)2 and the acceptor molecule C60 show a significant difference in the VOC of about 110 mV depending on whether the donor molecule exhibit an edge-on or face-on orientation. Here, we perform a detailed analysis of the losses determining the VOC in these devices. By analyzing EQE and EL spectra related to the CT state, we find the effect of donor orientation on the CT energy not to be sufficient to explain the full VOC difference. In accordance to this, we see almost no change of the HOMO energy in dependence of the orientation of the donor molecules. On the other hand, the absolute EL efficiency is significantly reduced in the bilayer cell with the edge-on oriented donor compared to the cell with face-on oriented donor molecules, pointing to increased non-radiative CT recombination.This shows that the molecular orientation can play a key role in determining non-radiative VOC losses in organic photovoltaics.