In situ morphology studies of the mechanism for solution additive effects on the formation of bulk heterojunction films
Type
ArticleAuthors
Richter, Lee J.
DeLongchamp., Dean M.
Bokel, Felicia A.
Engmann, Sebastian
Chou, Kang Wei
Amassian, Aram

Schaible, Eric G.
Hexemer, Alexander
KAUST Department
KAUST Solar Center (KSC)Material Science and Engineering Program
Organic Electronics and Photovoltaics Group
Physical Science and Engineering (PSE) Division
Date
2014-09-29Online Publication Date
2014-09-29Print Publication Date
2015-02Permanent link to this record
http://hdl.handle.net/10754/563765
Metadata
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The most successful active film morphology in organic photovoltaics is the bulk heterojunction (BHJ). The performance of a BHJ arises from a complex interplay of the spatial organization of the segregated donor and acceptor phases and the local order/quality of the respective phases. These critical morphological features develop dynamically during film formation, and it has become common practice to control them by the introduction of processing additives. Here, in situ grazing incidence X-ray diffraction (GIXD) and grazing incidence small angle X-ray scattering (GISAXS) studies of the development of order in BHJ films formed from the donor polymer poly(3-hexylthiophene) and acceptor phenyl-C61-butyric acid methyl ester under the influence of two common additives, 1,8-octanedithiol and 1-chloronaphthalene, are reported. By comparing optical aggregation to crystallization and using GISAXS to determine the number and nature of phases present during drying, two common mechanisms by which the additives increase P3HT crystallinity are identified. Additives accelerate the appearance of pre-crystalline nuclei by controlling solvent quality and allow for extended crystal growth by delaying the onset of PCBM-induced vitrification. The glass transition effects vary system-to-system and may be correlated to the number and composition of phases present during drying. Synchrotron X-ray scattering measurements of nanoscale structure evolution during the drying of polymer-fullerene photovoltaic films are described. Changes in the number and nature of phases, as well as the order within them, reveals the mechanisms by which formulation additives promote structural characteristics leading to higher power conversion efficiencies.Citation
Richter, L. J., DeLongchamp, D. M., Bokel, F. A., Engmann, S., Chou, K. W., Amassian, A., … Hexemer, A. (2014). In Situ Morphology Studies of the Mechanism for Solution Additive Effects on the Formation of Bulk Heterojunction Films. Advanced Energy Materials, 5(3), 1400975. doi:10.1002/aenm.201400975Sponsors
The authors wish to thank Jacquline Johnson and Edwin Chan for assistance in the development of the remote dispense system. Beamline 7.3.3 of the Advanced Light Source is supported by the Director of the Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.Publisher
WileyJournal
Advanced Energy Materialsae974a485f413a2113503eed53cd6c53
10.1002/aenm.201400975