title: A close look at charge generation in polymer:fullerene blends with microstructure control.
abstract: We reveal some of the key mechanisms during charge generation in polymer:fullerene blends exploiting our well-defined understanding of the microstructures obtained in pBTTT:PCBM systems via processing with fatty acid methyl ester additives. Based on ultrafast transient absorption, electro-absorption, and fluorescence up-conversion spectroscopy, we find that exciton diffusion through relatively phase-pure polymer or fullerene domains limits the rate of electron and hole transfer, while prompt charge separation occurs in regions where the polymer and fullerene are molecularly intermixed (such as the co-crystal phase where fullerenes intercalate between polymer chains in pBTTT:PCBM). We moreover confirm the importance of neat domains, which are essential to prevent geminate recombination of bound electron-hole pairs. Most interestingly, using an electro-absorption (Stark effect) signature, we directly visualize the migration of holes from intermixed to neat regions, which occurs on the subpicosecond time scale. This ultrafast transport is likely sustained by high local mobility (possibly along chains extending from the co-crystal phase to neat regions) and by an energy cascade driving the holes toward the neat domains.
authors: Institute of Chemical Sciences & Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL) , SB ISIC GR-MO, Station 6, CH-1015 Lausanne, Switzerland.
authors: Mariateresa
authors: M
authors: Scarongella
authors: Jelissa
authors: J
authors: De Jonghe-Risse
authors: Ester
authors: E
authors: Buchaca-Domingo
authors: Martina
authors: M
authors: Causa'
authors: Zhuping
authors: Z
authors: Fei
authors: Martin
authors: M
authors: Heeney
authors: Jacques-E
authors: JE
authors: Moser
authors: Natalie
authors: N
authors: Stingelin
authors: Natalie
authors: N
authors: Banerji
mesh_terms: D065966:Absorption, Physicochemical; D004583:Electrons; D037741:Fullerenes / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011108:Polymers / Q000737:chemistry*; D013499:Surface Properties; D013876:Thiophenes / Q000737:chemistry*
chemical_list: C539575:(6,6)-phenyl C61-butyric acid methyl ester; D037741:Fullerenes; D011108:Polymers; D013876:Thiophenes