ElectroOptical Properties of Polydiacetylene PDA Langmuir Films

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Electro-Optical Properties of Polydiacetylene
(PDA) Langmuir Films
O.Shusterman1 A.Vilan4, A. Berman3,4 Y.
Golan2,4 and B.Horovitz1,4
1Department of Physics 2Department of Materials
Engineering 3Department of Biotechnology
Engineering 4 Ilse Katz Center for Nanotechnology
Ben-Gurion University of the Negev, Beer-Sheva
84105, Israel
6th Students-Minerva Symposium on Molecular Based
Devices, 6-8 Mars, 2005
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Motivation

• PDA exists in two major phases which are
  different in
• their band gap (color) .

• Polydiacetylenes are particularly interesting
  conjugated polymers since they form nm thick
  and gt50µm wide single crystals

PDA is chemically flexible. Depending on its
side groups it can serve for bio-recognition as
well as organic/inorganic hybrid.
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Structure of PolyDiAcetylene
Hydrophobic tail
Diacetylene group
Hydrophilic head
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Preparing of sample
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Phase transition
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Phase transition
Y. Lifshitz
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Langmuir trouhg
UV lamp
Langmuir trough
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Electro-optical characterization
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Setup for absorption measurement
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Absorption of PDA film
p-p absorption band corresponding to S0 S1
transition
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Absorption as function of UV exposure
1.Blue phase Increased intensity of blue
phase Red-shift from 1.92 to 1.8eV with new
phonon peak 2. Appearance of red phase peak.
red phase
Blue phase
Energy, eV
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Photoluminescence of PDA film
X 102
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Nonliminescent decay in blue phase
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PHOTOLUMINECSENCE OF PDA
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Setup for photocurrent measurement
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Photocurrent in PDA films
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Photocurrent in PDA films
The photocurrent spectrum was observed at an
electric field ( E ) 106 V/ cm-1
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Conclusions

• We were able to measure dark and photo current
  through 10nm thick films at room temperature and
  under ambient conditions.
• Both the dark current and the photocurrent are
  higher for the red phase than for the blue phase
• The photocurrent spectrum differs from the
  absorption one an issue under current
  investigation
• Next aim measuring single domains chain
  alignment.

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Acknowledgements
Dr. Sofiya Kolushev ,BGU Roxana Golan,
BGU Juergen Jopp, BGU Nataly Belman,
BGU Yevgeniy Lifshitz, BGU
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Excitonic levels
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PHOTOLUMINECSENCE OF PDA
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PREPAIRING OF SAMPLE
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PHOTOLUMINECSENCE OF PDA
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PHOTOLUMINECSENCE OF PDA
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