Dresden 2011 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 24: Organic Electronics and Photovoltaics CPP-II (jointly with CPP, HL, and O)

DS 24.7: Vortrag

Dienstag, 15. März 2011, 12:15–12:30, ZEU 222

Towards Ideal Morphology of Polymer Bulk Heterojunction Solar Cells — •Chetan Raj Singh¹, Michael Sommer^2,3, Marcel Himmerlich¹, André Wicklein³, Stefan Krischok¹, Mukundan Thelakkat³, and Harald Hoppe¹ — ¹Institute of Physics, Ilmenau University of Technology, Germany — ²Department of Chemistry, University of Cambridge, United Kingdom — ³Applied Functional Polymers, University of Bayreuth, Germany

We present the thorough optimization of block copolymer (BCP) based polymer solar cells utilizing a blend of a self-assembling P3HT-b-PPerAcr BCP and an PPerAcr acceptor homopolymer. As an effect of increasing acceptor content in the block copolymer/homopolymer blend, we observe a continuous rise in the open circuit voltage (Voc) and the short circuit current (Isc) leading to an overall improved photovoltaic performance. The improved performance with increasing acceptor content is attributed to (a) an increase of the acceptor domain size leading to improved charge transport and to (b) a reduced recombination of charge carriers at the cathode interface due to the surface segregation of the acceptor. The surface segregation of the acceptor is identified by atomic force microscopy and X-ray photoelectron spectroscopy. Furthermore we show that by deliberately introducing an acceptor buffer layer at the cathode interface, we are able to control Voc at relatively high values (~ 640 mV), independently of the bulk heterojunction morphology underneath.