Enhance performance of organic solar cells based on an isoindigo-based copolymer by balancing absorption and miscibility of electron acceptor

Superior absorption of PC71BM in visible region to that of PC61BM makes PC71BM a predominant acceptor for most high efficient polymer solar cells (PSCs). However, we will demonstrate that power conversion efficiencies (PCEs) of PSCs based on poly[N,N'-bis(2-hexyldecyl)isoindigo-6, 6'-diyl-alt-thiophene-2,5-diyl] (PTI-1) with PC61BM as acceptor are 50% higher than their PC71BM counterparts under illumination of AM1.5G. AFM images reveal different topographies of the blends between PTI-1:PC61BM and PTI-1:PC71BM, which suggests that acceptor's miscibility plays a more important role than absorption. The photocurrent of 9.1 mA/cm(2) is among the highest value in PSCs with a driving force for exciton dissociation less than 0.2 eV. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3645622]