Berlin 2015 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 36: Organic Electronics and Photovoltaics: OPV II (joint session CPP, HL, TT)

CPP 36.10: Talk

Wednesday, March 18, 2015, 12:00–12:15, C 130

Effect of alcohol treatment on the morphology and performance of PTB7:PC71BM bulk heterojunction solar cells — Shuai Guo¹, Biye Cao¹, Weijia Wang¹, Jean-Francois Moulin², and •Peter Müller-Buschbaum¹ — ¹TU München, Physik-Department, LS Funktionelle Materialien, James-Franck-Str. 1, 85748 Garching — ²Helmholtz-Zentrum Geesthacht am MLZ, Lichtenbergstr. 1, 85747 Garching

The environmentally friendly alcohol treatment of bulk heterojunction (BHJ) polymer solar cells using the low bandgap copolymer based on thieno[3,4-b]thiophene-alt-benzodithiophene units (PTB7) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) is studied. Different alcohols are tested and besides the most commonly used methanol treatment, other alcohols such as ethanol, 2-propanol, and 1-butanol also improve the device performance as compared to untreated solar cells. Changes of the surface structure caused by the alcohol treatment are probed with AFM and the modification of inner film morphology is probed by time of flight-grazing incidence small angle neutron scattering (TOF-GISANS). UV/Vis measurements show that the thickness of all BHJ films remains unchanged by the different solvent treatments. Thus, the enhanced device performance induced by the alcohol treatments is correlated to the reconstruction of the inner film structures probed with TOF-GISANS and the modified energy levels at the interfaces between the BHJ layer and the aluminum electrodes, evident by the enhanced short-circuit current and open-circuit voltage of the I-V curves.