The addition of a block copolymer to the polymer/fullerene blend is a novel approach to the fabrication of organic solar cells. The block copolymer (P3HT-b-P4VP) is used as nanostructuring agent in the active layer. A significant enhancement of the cell efficiency is observed, in correlation with morphology control, both before (as-cast) and after the annealing process.

International audienceWe report the increased crystallization of poly(3-hexylthiophene) (P3HT) in the donor-acceptor mixture of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) with P3HT by the addition of a block copolymer, P3HT-b-PI, where PI refers to polyisoprene. The photovoltaic performance of devices created using this blend is markedly improved by the addition of the diblock copolymer. We have characterized the structure of thin films of the P3HT-b-PI containing mixtures using optical microscopy, scanning force microscopy, UV-vis absorption spectroscopy, neutron reflectometry, and grazing incidence X-ray diffraction (GIXD). The GIXD data provide the information on the crystallinity of the films, the absorption data were used to confirm that the addition of the diblock was responsible for the increase in crystallization, neutron reflectometry data reveal a PCBM-rich region near the hole injection layer, and the two microscopy techniques revealed the structural effect of the crystallization at the surface of the films

A well-defined and monofunctional poly(3-hexylthiophene)-based (P3HT) macroinitiator has been obtained through a clean, simple, and an efficient multistep synthesis process. The macroinitiator is obtained via intermolecular radical 1,2addition onto an x-acrylate-terminated P3HT macromonomer. In a second step, well-defined rod-coil block copolymers were obtained by nitroxide-mediated radical polymerization (NMRP) using the so-called Blocbuilder V R . The polymerization was found to be controlled with various monomers such as styrene, isoprene, 4-vinylpyridine, or methyl acrylate. This process constitutes a very promising way to obtain versatile and clean materials for organic electronics. EXPERIMENTAL MaterialsAll reactions were carried out under a nitrogen atmosphere. Monomers (styrene, methyl acrylate (MA), 4-vinylpyridine (4VP), methyl methacrylate (MMA), isoprene) were distilled over calcium hydride under reduced pressure. BlocBuilder V R (MAMA-SG1) was kindly provided by Arkema (France).Additional Supporting Information may be found in the online version of this article.