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Name (Title):
Fumio S. Ohuchi Professor, Associate Chair of Department
(Research Director of NIMS Overseas Operation Office at UW)
Affiliation:
Department of Material Science & Engineering
College of Engineering, University of Washington
Address:
311 Roberts Hall, Seattle, WA 98195-2120
Email: ohuchi@u.washington.edu
Home Page: http://depts.washington.edu/mse/people/faculty/faculty_Ohuchi.htm
Presentation Title:
Polymer Blends for Nano-structured Photovoltaic Effect
Abstract:
Polymer-based solar cells have the potential for large-scale power generation based on
materials that provide the possibility of inexpensive, lightweight, flexible. Since the discovery of
the photoinduced electron transfer from a conjugated polymer to fullerene molecules, followed
by the introduction of the bulk hetero-junction concept, this material combination has been
extensively studied in organic solar cells, leading to several breakthroughs in efficiency, with a
power conversion efficiency approaching 5%.
Our research focuses on the physical chemistry of nanostructured materials with potential
applications in low cost photovoltaics (solar cells). We study conjugated semiconducting polymer
blends such as poly-[2-(3,7-dimethyloctyloxy)-5-methoxy-p-phenylenevinylene] (MDMO-PPV),
poly-3-hexylthiophene (P3HT), with the fullerene derivative, [6,6]-phenyl-C61-butyric acid
methyl ester (PCBM). It has been found that the patterned surface chemistry helps greatly to
tailor the film morphology of solution-processed donor/acceptor polymer blends on the
microscale and nanoscale. We create substrates with patterned monolayers on indium tin oxide
(ITO) surfaces using microcontact printing and Dip-Pen Nanolithography (DPN) to pattern
functional groups with both micro- and nanoscale features. Spin-coating method is developed to
fabricate polymer:PCBM films onto these substrates, followed by thermal annealing under
nitrogen, leads to the formation of structured polymer films. Although there are many challenges
to develop efficient ordered heterojunctions, it is considered that the most efficient ordered
nanostructured polymer device is very significant for enhancing the mobility of polymer solar
cell. This program is performed by using SPM technology developed in NIMS under the
collaboration with Prof. D.Ginger from Department of Chemistry and Dr. X. Liu from Materials
Science & Engineering of UW.
Figures are AFM ac-mode topographic (left) and fluorescence (right) images of P3HT:PCBM
films spin-coated on OPA-patterned substrates. Both show a segregation of P3HT-enriched in the
dark area, and PCBM-enriched in the bright area.
Film thickness of ~150 nm, excitation at
535-565 nm, emission at 590 nm.
Poster Session PM-17
References:
A. C. Mayer, S. R. Scully, B. E. Hardin, M. W. Rowell, and M. D. McGehee*, Materialstoday 10,
28 (2007).
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