Interplay Between Side Chain Pattern, Polymer Aggregation, and Charge Carrier Dynamics in PBDTTPD:PCBM Bulk-Heterojunction Solar Cells

被引:62
作者
Dyer-Smith, Clare [1 ]
Howard, Ian A. [1 ]
Cabanetos, Clement [2 ]
El Labban, Abdulrahman [2 ]
Beaujuge, Pierre M. [2 ]
Laquai, Frederic [1 ]
机构
[1] Max Planck Inst Polymer Res, Max Planck Res Grp Organ Optoelect, D-55128 Mainz, Germany
[2] King Abdullah Univ Sci & Technol, Div Phys Sci & Engn, Chem Sci & Mat Sci & Engn, Thuwal 239556900, Saudi Arabia
关键词
EXCITED-STATE; MORPHOLOGY; RECOMBINATION; GENERATION; PHOTOGENERATION; DEPENDENCE; BLENDS;
D O I
10.1002/aenm.201401778
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Poly(benzo[1,2-b:4,5-b'] dithiophene-alt-thieno[3,4-c] pyrrole-4,6-dione) (PBDTTPD) polymer donors with linear side-chains yield bulk-heterojunction (BHJ) solar cell power conversion efficiencies (PCEs) of about 4% with phenyl-C-71-butyric acid methyl ester (PC71 BM) as the acceptor, while a PBDTTPD polymer with a combination of branched and linear substituents yields a doubling of the PCE to 8%. Using transient optical spectroscopy it is shown that while the exciton dissociation and ultrafast charge generation steps are not strongly affected by the side chain modifi cations, the polymer with branched side chains exhibits a decreased rate of nongeminate recombination and a lower fraction of sub-nanosecond geminate recombination. In turn the yield of long-lived charge carriers increases, resulting in a 33% increase in short circuit current (J(sc)). In parallel, the two polymers show distinct grazing incidence X-ray scattering spectra indicative of the presence of stacks with different orientation patterns in optimized thin-film BHJ devices. Independent of the packing pattern the spectroscopic data also reveals the existence of polymer aggregates in the pristine polymer films as well as in both blends which trap excitons and hinder their dissociation.
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页数:11
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