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Please use this identifier to cite or link to this item: http://hdl.handle.net/1942/14451

Title: Charge transfer in the weak driving force limit in blends of MDMO-PPV and dithienylthiazolo[5,4-d]thiazoles towards organic photovoltaics with high V-OC
Authors: Nevil, Nissy
Ling, Yun
Van Mierloo, Sarah
Kesters, Jurgen
Piersimoni, Fortunato
Adriaensens, Peter
Lutsen, Laurence
Vanderzande, Dirk
Manca, Jean
Maes, Wouter
Van Doorslaer, Sabine
Goovaerts, Etienne
Issue Date: 2012
Citation: PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 14 (45), p. 15774-15784
Abstract: A series of three 5'-aryl-2,5-dithienylthiazolo[5,4-d]thiazole (DTTzTz) semiconducting molecules with different aryl substituents has been investigated as alternative acceptor materials in combination with the donor polymer poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene] (MDMO-PPV) in order to evaluate the photoinduced charge transfer (CT) efficiency in the resulting blends, designed towards possible application in organic photovoltaics. Photoluminescence quenching together with polaron detection by electron paramagnetic resonance and photoinduced absorption (PIA) demonstrate an increasing charge transfer efficiency when the DTTzTz substituents are varied from thien-2-yl to 4-trifluoromethylphenyl and 4-cyanophenyl groups, correlating well with the increasing acceptor strength in this series of molecules. In line with this observation, there is a decrease in the effective optical bandgap relative to pure MDMO-PPV that becomes more pronounced along this series of acceptor compounds, reaching 0.12 eV in the blend with 4-CN-Ph-DTTzTz. Intermolecular interactions between the blend components lead to lower energy transitions which are found to contribute significantly to the device external quantum efficiency. The high V-OC reached in devices based on MDMO-PPV: 4-CN-Ph-DTTzTz blends meets the expectations for such a donor: acceptor combination. However, thermal activation of charge carrier recombination occurs because of the weak driving force for charge transfer, as shown by time-dependent PIA measurements, and this is suggested as a cause for the observed low photovoltaic performance.
Notes: [Nevil, Nissy; Ling, Yun; Van Doorslaer, Sabine; Goovaerts, Etienne] Univ Antwerp, Dept Phys, B-2610 Antwerp, Belgium. [Piersimoni, Fortunato; Manca, Jean] Hasselt Univ, Inst Mat Res IMO IMOMEC, Organ Nanostruct Elect & Energy Convers ONE2, B-3590 Diepenbeek, Belgium. [Lutsen, Laurence; Vanderzande, Dirk] IMOMEC Ass Lab, IMEC, B-3590 Diepenbeek, Belgium.
URI: http://hdl.handle.net/1942/14451
DOI: 10.1039/c2cp42399e
ISI #: 000310460400019
ISSN: 1463-9076
Category: A1
Type: Journal Contribution
Validation: ecoom, 2013
Appears in Collections: Research publications

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