Polymer/fullerene bulk heterojunction solar cells use an interpenetrating network of π-conjugated electron-donor polymers and electron-acceptor C60 as photo-active layer. Currently, the most investigated blends are constituted of regioregular poly(3-hexylthiophene) (rr-P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). The nanostructured active layer determines to great extend the overall performance of the devices. First of all, we introduced rod-coil block copolymers as compatibilizer into P3HT:PCBM blends and investigate their influence on the blend morphology and the related photovoltaic performance. Two P3HT-based block copolymer families have been studied. The first one has a C60-grafted poly-butylacrylate coil block and the second one is based on poly(4-vinylpyridine) (P4VP) coil block. The film morphology and device efficiencies are investigated as a function of copolymer content, P3HT/PCBM mass ratio and coil nature. A second possible route to obtain a stable donor/acceptor nanostructure consists of using semiconductor block copolymers as photoactive layer, since these materials are able to self-assemble into donor/acceptor heterojunctions by microphase separation. We explored P3HT-P4VP rod-coil block copolymers blended with PCBM in view of their utilization in photovoltaic devices. The copolymer self-assembles into nano-domains rich in either P3HT or P4VP, while the strong chemical affinity of P4VP with PCBM leads to an accumulation of the latter in the P4VP domains, providing them a acceptor character. It is found that organized and thermally stable thin films, that exhibit ambipolar field effect mobilities, can be achieved for a specific rod/coil ratio.
