Optical Spectroscopic Studies of Polyfluorene and its Copolymers
Hiroyoshi Naito
Department of Physics and Electronics, Osaka Prefecture University
Sakai, Osaka, 599-8531, Japan
Corresponding author email: naito@pe.osakafu-u.ac.jp
Conjugated polymers are an important class of electronic and photonic materials, having a
variety of possible applications such as active materials in light-emitting diodes and displays, lowcost photovoltaics and printable electronics. The conjugated polymer poly(9,9-dioctylfluorene)
(F8) can be viewed as model system for studying the effect of molecular conformation of a
conjugated polymer on its electronic and photonic properties. Such studies are made possible by
the fact that F8 can be prepared in three distinguishable classes of conformational isomers with
different average backbone chain length [1]: these classes have been termed the phase (the glassy
state), the phase (the crystalline phase), and a single unique conformational isomer termed the
phase.
The electronic and photonic properties of F8 and F8 based copolymers discussed here are
studied by optical spectroscopy, including absorption, photoluminescence, time-resolved
photoluminescence, and photoconductivity. The following issues are discussed in terms of these
spectroscopic studies:
i) Absorption and photoluminescence spectra of the three phases of F8 [1]
ii) Amplified spontaneous emission [2]
F8 and some of F8 based copolymers are gain media, and the amplified spontaneous
emission is observed. The phase F8 is shown to have the highest gain coefficient
and the lowest loss coefficient among the three phases.
iii) Electroabsorption [3]
iv) Photoinduced absorption
Singlet and triplet excited structures of F8 have been determined by electroabsorption
and photoinduced absorption spectroscopies. The information is important for device
design of light-emitting diodes; the injection barrier between F8 and cathode
interface, and the doping of triplet as well as singlet emitters to F8.
v) Photoinduced degradation [4]
Photoinduced oxidation of F8 creates fluorenone units in F8, which reduce the
luminescence efficiency and degrade the colour purity of F8. An origin of the
degradation is shown to be the formation of exciplexes between fluorenone units and
nearest F8 chains.
vi) Polarized absorption and photoluminescence [5]
A method is shown to prepare aligned phase F8, from which high efficient,
polarized light-emitting diodes can be fabricated.
[1] K. Asada, T. Kobayashi and H. Naito, Jpn. J. Appl. Phys. 45, L247-L249 (2006)
[2] H. Azuma, T. Kobayashi, Y. Shim, N. Mamedov, and H. Naito, Organic Electronics 8, 184
(2007).
[3] S. Ikame, T. Kobayashi, S. Murakami, and H. Naito, Phys. Rev. B 75, 035209 (2007).
[4] K. Asada, H. Takahashi and H. Naito, Thin Solid Films 509, 202-206 (2006)
[5] T. Endo, T. Kobayashi, T. Nagase, and H. Naito, Jpn. J. Appl. Phys. 46, L1093 (2007).
--------------------------------------------PRIMARY TOPIC: J
SECONDARY TOPIC: A4
THIRD TOPIC: .L
PREFERRED FORMAT OF PRESENTATION (ORAL/POSTER): ORAL: Invited
--------------------------------------------Corresponding author name: Hiroyoshi NAITO
Corresponding author email: naito@pe.osakafu-u.ac.jp
TOPICS
Please choose primary and secondary topics
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Optical properties of materials
A1
General
A2
Crystals
A3
Polycrystalline bulk and film
A4
Amorphous and organics
A5
Nanostructures, including photonic crystals
Preparation and Characterization of Quantum Dots, Quantum Wires and
Other Quantum Structures
Excitonic Processes
Luminescence, Phosphors, Scintillators and Applications
Photoinduced Effects and Applications
Photoconductivity and Photogeneration
Nonlinear Optical Effects and Applications
Electro-Optic Effects and Applications
Glasses for Optics, Optoelectronics and Photonics (including ZBLAN,
fluozirconate, oxyfluoride and other glasses)
Polymers for Optics, Optoelectronics and Photonics
Semiconductors for Optoelectronics
J1
Semiconductors for Optoelectronics: Wide Bandgap
J2
Semiconductors for Optoelectronics: Narrow Bandgap
J3
Semiconductors for Optoelectronics: Heterostructures
Light Emitting Devices (including organics)
Photonic and Optoelectronic Materials and Devices (including devices for
telecommunications, laser and detectors)
Optical Storage
Photovoltaics (materials and devices, and their properties)
Waveguides and Integrated Photonics
Silicon Photonics
Optical Fibers and Fiber Sensors
Experimental Techniques
Femtosecond Spectroscopy
Teraherz (THz) techniques, including materials, emitters and detectors
Defect Spectroscopy
Plasmons and Surface Plasmons
Selected Topics (e.g. Photocatalysts in Materials, Materials for Energy
Conversion etc)
Abstract submission
Deadline: 31 March, 2008
Note: Late abstracts may be considered at the discretion of the conference
organizers.
Abstract acceptance: 15 April 2008 (Tentative)
Manuscripts: To be submitted either before or during the conference using the
instructions on the conference website