1. Substantially Conductive Polymers
Behzad Pourabbas
Dep. Of Polymer eng.
Sahand University of Technology
Tabriz-Iran

2. In order to download the PPT files:
1- Go to SUT web page (
2- find the Polymer eng. Faculty (
3- Go to my page: (
4- Education  Courses Ph.D Materials for IT (
5- Download the files: (
Using the file contents are allowed by referencing.
11/28/2018

3. Overview Discovery and history The story of Polyacetylene
Structural Characteristics
Doping Concept
The Charge Carriers
Applications
11/28/2018

4. The discoverers, the Noble laureates (Chem 2000)
11/28/2018

5. 11/28/2018

6. Materials, According To Electrical Properties
insulator,
<10-7S/cm
semiconductor,
S/cm depending upon doping degree
conductor and
>103 S/cm
superconductor
11/28/2018

7. Polymers and Conductivity
Since discovery of conductive polyacelene (PA) doped with iodine, a new field of conducting polymers, which is also called as “synthetic metals”, has been established and earned the Nobel Prize in Chemistry in 2000.
In 1977, this accidentally discovered that insulating π- conjugated PA could become conductor with a conductivity of 103 S/cm by iodine doping.
11/28/2018

8. The story of PA
11/28/2018

9. The Story of Polyacetylene
PA could be regarded as an excellent candidate of polymers to be imitating a metal.
Because it has alternating double and single bonds, as called conjugated double bonds.
11/28/2018

10. The Story of Polyacetylene
At the beginning of the 1970s, Hedeki Shirakawa at Tokyo Institute of Technology, Japan, was studying the polymerization of acetylene into plastics by using catalyst created by Ziegler-Natta.
A visiting scientist in Shirakawa’s group tried to synthesize PA in the usual way. However, a beautifully lustrous silver colored film, rather than the black powder synthesized by the conventional method, was obtained.
11/28/2018

11. The Story of Polyacetylene
Shirakawa finally found that the catalyst concentration used was enhanced by 103 times! Shirakawa was stimulated by the accidental discovery and further found the molecular structure of the resulting PA was affected by reaction temerature, for instance, the silvery film was trans-polyacetylene whereas copper-colored film was almost pure cis-polyacetylene.
11/28/2018

12. The Story of Polyacetylene
In another part of the world, chemiste Alan G. MacDiarmid and physicist Alan J. Heeger at University of Pennsylvania, Philadephia, USA were studying the first metal-like inorganic polymer sulfur nitride ((SN)x ), which is the first example of a covalent polymer without metal atoms. In 1975, Prof. MacDiarmid visited Tokyo Institute of Technology and gave a talk on (SN)x. After his lecture, MacDiarmid met Shirakawa at a coffee break and showed a sample of the golden (SN)x to Shirakawa. Consequently, Shirakawa also showed MacDiarmid a sample of the silvery (CH)x.
11/28/2018

13. The Story of Polyacetylene
The beautiful silvery film caught the eyes of MacDiarmid and he immediately invited Shirakawa to the University of Pennsylvania PA.
Since MacDiarmid and Heeger had found previously that the conductivity of (SN)x could be increased by 10 times after adding bromine to the golden (SN)x material, which is called as “doping” item in inorganic semiconductor.
Therefore, they decided to add some bromine to the silvery (CH)x films to see what happens.
Miracle took place on November 23, 1976!
At that day, Shirakawa worked with Dr. C.K. Chiang, a postdoctoral fellow under Professor Heeger, for measuring the electrical conductivity of PA by a four-probe method.
11/28/2018

14. The Story of Polyacetylene
Surprise to them, the conductivity of PA was ten million times higher than before adding bromine. This day was marked as the first time observed the “doping” effect in conducting polymers.
In the summer of 1977, Heeger, MacDiarmid, and Shirakawa co-published their discovery in the article entitled “Synthesis of electrically conducting organic polymers: Halogen derivatives of polyacetylene (CH)n” in The Journal of Chemical Society, Chemical Communications.
11/28/2018

15. Structural Characteristics and Doping Concept
11/28/2018

16. Structural Characteristics and Doping Concept!
11/28/2018

17. 11/28/2018

18. 11/28/2018

19. The concept of Doping
11/28/2018

20. 11/28/2018

21. Discovery of the First Conducting Polymer
11/28/2018

22. 11/28/2018

23. 11/28/2018

24. 11/28/2018

25. 11/28/2018

26. 11/28/2018

27. The Charge Carriers
11/28/2018

28. 11/28/2018

29. 11/28/2018

30. 11/28/2018

31. 11/28/2018

32. Usually, soliton is served as the charge carrier for a degenerated conducting polymer (e.g. PA) whereas polaron or bipolaron is used as charge carrier in a non-degenerated conducting polymer (e.g. PPy and PANI)
Schematic structure of (a) a positive polaron, (b) a positive bipolaron,
and (c) two positive bipolarons in polythiophenes
11/28/2018

33. Typical Charge Carriers (via doping)
11/28/2018

34. Chemical term, charge and spin of soliton, polaron and bipolaron in
conducting polymers
11/28/2018

35. 11/28/2018

36. 11/28/2018

37. 11/28/2018

38. Rechargeable batteries Radar absorbers
Filtration, membranes
Rechargeable batteries
Radar absorbers
11/28/2018

39. Applications
11/28/2018

40. Potential applications and corresponding physical properties of conducting Polymers.
11/28/2018

41. 11/28/2018

42. Organic Light Emitting Polymer
First reported in 1990 (Nature 1990, 347, 539)
Based on poly(p-phenylenevinylene) (PPV), with a bandgap of 2.2 eV
ITO: Indium-tin-oxide -A transparent electrical conductor
11/28/2018

43. Threshold for charge injection (turn-on voltage): 14 V (E-field = 2 x 106 V/cm)
Quantum efficiency = 0.05 %
Emission color: Green
Processible ? No!!
Polymer is obtained by precursor approach. It cannot be redissolved once the polymer is synthesized
11/28/2018

44. Other PPV Derivatives MEH-PPV
More processible, can be dissolved in common organic solvents (due to the presence of alkoxy side chains)
Fabrication of Flexible light-emitting diodes (Nature 1992, 357, 477)
11/28/2018

45. Substrate: poly(ethylene terephthlate) (PET)
Anode: polyaniline doped with acid-a flexible and transparent conducting polymer
EL Quantum efficiency: 1 %
Turn-on voltage: 2-3 V
11/28/2018

46. Other Examples of Light Emitting Polymers
Poly(p-phenylene) (PPP)
BLUE light
emission
Poly(9,9-dialkyl fluorene)
CN-PPV: RED light emission
Nature 1993, 365, 628
Polythiophene derivatives
A blend of these polymers produced variable colors, depending on the composition
Nature 1994, 372, 443
11/28/2018

47. Applications
Flat Panel Displays: thinner than liquid crystals displays or plasma displays (the display can be less than 2 mm thick)
Flexible Display Devices for mobile phones, PDA, watches, etc.
Multicolor displays can also be made by combining materials with different emitting colors.
11/28/2018

48. Photodiode For an Electroluminescence process: Electrons Photons
Can we reverse the process?
Photons
Electrons
YES!
Photodiode
Production of electrons and holes in a semiconductor device under illumination of light, and their subsequent collection at opposite electrodes.
Light absorption creates electron-hole pairs (excitons). The electron is accepted by the materials with larger electron affinity, and the hole by the materials with lower ionization potential.
11/28/2018

49. A Two-Layer Photovoltaic Devices
Conversion of photos into electrons
Solar cells (Science 1995, 270, 1789; Appl. Phys. Lett. 1996, 68, 3120)
(Appl. Phys. Lett. 1996, 68, 3120)
490 nm
Max. quantum efficiency: ~ 9 %
Open circuit voltage Voc: 0.8 V
11/28/2018

50. MEH-PPV e- h+ C60 Another example: Science 1995, 270, 1789.
ITO/MEH-PPV:C60/Ca
Active materials: MEH-PPV blended with a C60 derivative
light
MEH-PPV
ITO/MEH-PPV:C60/Ca
dark e- h+
light
C60
ITO/MEH-PPV/Ca
dark
11/28/2018

51. A Photodiode fabricated from polymer blend
(Nature 1995, 376, 498)
Device illuminated at 550 nm (0.15 mW/cm2)
Open circuit voltage (Voc): 0.6 V
Quantum yield: 0.04 %
11/28/2018

52. Field Effect Transistors (FET)
Using poly(3-hexylthiophene) as the active layer
“All Plastics” integrated circuits (Appl. Phys. Lett. 1996, 69, 4108; recent review: Adv. Mater. 1998, 10, 365)
11/28/2018

53. More Recent Development
Use of self-assembled monolayer organic field-effect transistors
Possibility of using “single molecule” for electronic devices
(Nature 2001, 413, 713)
11/28/2018

54. Prof. Heflin's group is developing organic solar cells that have the potential to be flexible, lightweight, efficient renewable energy sources. Photograph by John McCormick.
Polymer light-emitting diodes, such as the one produced by Martin Drees (Ph.D. 2003) in Prof. Heflin's laboratory, may potentially yield flexible, inexpensive flat-panel displays.
11/28/2018

55. Prof. Heflin's group is examining how nanoscale control of the composition of organic solar cells consisting of semiconducting polymers and fullerenes can improve their power conversion efficiency.
Prof. Heflin's group is using self-assembly of nanoscale organic films to create organic electrochromic devices that change color when a voltage is applied at rates up to 50 Hz.
11/28/2018

56. Prof. Heflin's group is using self-assembly of nanoscale organic films to create organic
electrochromic devices that change color when a voltage is applied at rates up to 50 Hz.
11/28/2018

57. 11/28/2018

58. Conductive Coatings
Replacement for ITO glass
11/28/2018

59. Conductive Coatings
Replacement for ITO glass
11/28/2018

60. Conductive Coatings
Replacement for ITO glass
11/28/2018

61. Synthesis
Information Available for interested Students
11/28/2018

62. Electropolymerization
Information Available for Interested Students
11/28/2018

63. The End
11/28/2018