1 Introduction_________________________________________ 4

2 Experimental________________________________________ 10

2.1 Electronic equipment 10

2.1.1 Conventional electrochemical techniques 11

2.1.2 Impedance measurements 11

2.1.3 Impedance measurements on the twin electrode 12

2.2 Cells and Electrodes 14

2.2.1 Three-electrodes-cell 14

2.2.2 The twin electrode 15

2.3 Chemicals and Electrolytes 16

3 Basic experimental data analysis________________________ 17

3.1 The analysis of the impedance spectra of conducting polymer layers 17

3.1.1 Monolayer of an electroactive species 17

3.1.2 Homogenous nonporous electroactive layers 19

3.1.3 Porous electroactive layers 21

3.2 Field considerations for measurements on the twin electrode 25

3.3 Complex nonlinear least squares fitting 28

4 Results____________________________________________ 30

4.1 Impedance measurements during oxidation and reduction of conducting polymers 30

4.1.1 Simulation procedure 30

4.1.2 Measurements and simulation results 31

4.2 Impedance measurements on twin working electrodes bridged with polybithiophene layers 37

4.2.1 Verification of the measurement set-up 37

4.2.2 Impedance spectra 39

4.2.3 Estimations of conductivity and thickness of the polymer layer 46

4.3 The thickness dependence of the impedance spectra of polybithiophene layers measured under galvanostatic condition 48

4.3.1 Measurement results 48

4.3.2 Data processing 52

4.4 Impedance investigation of conducting polymer layers considering their inhomogeneity. 57

4.4.1 Model of an inhomogeneous porous electroactive layer 57

4.4.2 Experimental results and validation of the model 63

5 Discussion__________________________________________ 71

5.1 The contribution of faradaic currents in the oxidation/reduction of polybithiophene and polypyrrole during cyclic voltammetry experements. 71

5.1.1 Polybithiophene. 72

5.1.2 Polypyrrole. 74

5.2 Contribution of electronic and ionic resistance to the resistive hindrance of the recharge processes of polybithiophene 74

5.3 Evaluation of kinetic relevant parameters of conducting polymers by analysis of layers with different thickness. 76

5.4 Influence of inhomogeneity on the electrochemical behavior of conducting polymer layers. 79

6 Conclusion_________________________________________ 83

7 Acknowledgments____________________________________ 85

8 References_________________________________________ 89