Polyfluorene Derivative with Multifunctional Side Chains for Lightemitting Electrochemical Cell

1
Polyfluorene Derivative with Multifunctional
Side Chains for Light-emitting Electrochemical
Cell

• Doojin Park, Dongyu Kim
• Department of Materials Science and Engineering
• Kwangju Institute of Science and Technology

2
What is LEC?

• Luminescent polymer with ionic species for doping
  and ionically conductive material
• When sufficient voltage is applied between
  electrodes, electrochemical doping is initiated
  by ion migration and p-i-n junction is created in
  situ
• The created p-i-n junction shows behavior like
  inorganic p-n diode with ohmic contact

Q. Pei et al., J. Am. Chem. Soc., 118(1996)
3
LEC vs. LED

• LED
• Field driven
• High turn on voltage
• Sensitive to thickness
• Sensitive to contact

• LEC
• Voltage driven
• Low turn on voltage
• Not sensitive to thickness
• Not Sensitive to contact

J. Kalinowski, J. Phys. DAppl. Phys, 32(1999)
4
Fixed Junction

• Common p-i-n junction called dynamic junction
  will disappear by discharging after the
  external bias has been removed slow
  response hysteresis behavior
• The created junction could be fixed by some
  method like cooling far below Tg or crosslinking
• For fixed p-i-n junction LEC, we introduced
  crosslinkable and ion conducting functional side
  chain into polyfluorene

5
Synthesis of Polyfluorene Derivative
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NMR
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Absorption PL Spectra
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Photoluminescence Spectra with Different
Annealing Temperature
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Conclusion

• We introduced crosslinkable and ion conducting
  side chain into polyfluorene
• The functionalized polyfluorene derivative can be
  used as a LEC material
• After epoxydation, the polymer emit green light
  instead of blue light
• We found that this red-shift caused by
  aggregation from PL spectra with different
  annealing temperature

10
References

• Q. Pei, G. Yu, C. Zhang, Y. Yang, and A. J.
  Heeger, Science, 269, 1086(1995)
• Q. Pei, Y. Yang, G. Yu, C. Zhang, and A. J.
  Heeger, J. Am. Chem. Soc. 118, 3922(1996)
• J. Gao, Y. Li, G. Yu, and A. J. Heeger, J. Appl.
  Phys., 86, 4594(1999)
• Y. Yang and Q. Pei, J. Appl. Phys., 81,
  3294(1997)
• G. Klaerner and R. D. Miller, Macromolecules, 31,
  2007(1998)