Dresden 2014 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 19: Poster Session 1 (joint session with BP)
CPP 19.57: Poster
Dienstag, 1. April 2014, 09:30–13:00, P1
Surface structure of organic solar cells based on PBDTTT-C and PC71BM — •Mario Zerson1, Andreas Zusan2, Björn Gieseking2, Carsten Deibel2, and Robert Magerle1 — 1Fakultät für Naturwissenschaften, Technische Universität Chemnitz, Chemnitz, Germany, — 2Experimental Physics VI, Julius-Maximilians-University of Würzburg, Würzburg, Germany
We study the surface structure of organic heterojunction solar cells based on blends of poly[4,8-bis-(2-ethylhexyloxy)-benzo[1,2-b:4,5-b']dithiophene-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thie-no[3,4-b]thiophene))-2,6-diyl] (PBDTTT-C) and PC71BM with a weight ratio of 1:1,5. The co-solvent diiodooctane (DIO) was used with ratios between 0% and 10% to increase the solubility of PC71BM. Thin films spun cast with different amounts of DIO exhibit different power conversion efficiencies and surface morphologies. We investigate the latter with amplitude modulation atomic force microscopy (AFM). Conventional AFM height and phase images are complemented with data obtained from maps of amplitude-phase-distance (APD) curves. This allows us to determine the unperturbed (true) surface and the mechanical properties of the top surface layer of the specimens. For describing and quantifying the surface morphology we use different morphological measures. We discuss the structure formation process of the blends in terms of intermixing and demixing of the donor and acceptor material during spin casting, the size of the interfacial area between donor and acceptor components, and the formation of percolation pathways for the charge carriers.