Chapter 3. Organic Conductor

Conductivity Of Organic Materials

Conductivity  = en  n: number of carriers; m: mobility of the carriers

Electronic structures of Organic Molecules (1) Core electrons. (2)  electrons, localized between two atoms. (3) n electrons, located at a particular heteroatom, usually have high orbital energy and could be promoted easily. (4)  electrons, delocalized over an array of atoms, usually have high MO energy and could be promoted easily.

Discovery of Conducting Organic Crystals

Conductivity is controlled by the phthalocyanine ring. The metal core does not interfere the conductivity. Phthalocyanine channel I-I-

Chain length: Si:120  30 Ge: 74  40 Sn:100  40

Conjugated Polymers

Polyacetylene

(1) Could a charge through delocalize through the  array? (2) Is there any one dimensional conductor in principle? (3) How a charge hop from one  array to another adjacent  array?

Electrical conductivity of polyacetylene Cis-PA  = 1.7 x S/cm Trans-PA  = 4.4 x S/cm I 2 doped  = 5.5 x 10 2 S/cm AsF 5 doped  = 1.2 x 10 3 S/cm Electrochemical Oxidation  = 1 x 10 3 S/cm Li doped  = 2 x 10 2 S/cm Na doped  = S/cm

Polyparaphenylene (PPP)

Drawbacks: low solubility. Alkyl side chain for enhancing solubility

When no of phenylene units is larger than 12, the material becomes metallic after doped

Synthesis of Polythiophenes PEDOT.PSS

Polyaniline (PANI) Conductor Insulator

Preparation

Doping and Undoping PANI doped with H 3 PO 4 was found to be most stable.

Conductivity could go up to S/cm after doping

Poly-4-phenylene-(E)-vinylene (PPV) Highly insoluble Precursor for thin film formation

Knoevenagel Condensation Wittig Horner reaction Hsieh, B. R. (Xerox)

Lithium Battery

Rechargeable Battery With PA electrode Oxidation (CH) x +xy(ClO 4 - ) [(CH) +y (ClO 4 - ) y]x + xye - Reduction (CH) x +xy(Li + ) + xye - [(CH) -y (Li + ) y]x

Battery Structures based on PA (a)P type (CH) x anode/Li cathode (b)P type (CH) x anode/n type (CH) x cathode (c)n type (CH) x anode /Li cathode When the battery is doped at 6%, the Voltages are 3.7, 2.5, 1.2V respectively

Rechargeable Battery with poly-4-phenylene electrode

Organic Photoconductors

Scher-Montrol Theory on dispersive photocurrent

Organic Photoconductors (1) Conjugated polymers (2) Polymers containing aromatic side-chains (3) Small molecules

Organic Solar Cell

Example

Self-Organized Discotic Liquid Crystals for High-Efficiency Organic Photovoltaics