Abstract
The current-voltage (I-V) relationship in semi-conductive conjugated polymer is usually analyzed by the Mott-Gurney equation. In the derivation of the Mott-Gurney equation, constant carrier mobility, and single-carrier as well as trap–free space charge limited transport are assumed. While the Mott-Gurney equation predicts quadratic I-V relationship, power law with exponent larger than three is often observed in experimental data. The deviation between experiments and theory is usually attributed to the dependence of mobility on electric field. A typical way to analyze the data is to substitute the field-dependent mobility into the square law equation directly. However, this is inconsistent with the constant mobility assumption in the derivation of Mott-Gurney equation. Although extensive numerical modeling of charge transport in conjugated polymers is available, a simplified yet logically-consistent closed-form solution is useful to analyze field-dependent of carrier mobility. In this thesis, we take field-dependent mobility into account and successfully derive a closed-form current density-voltage equation (J-V equation). Based on this new theoretical model, the current density is found to be globally proportional to Vm, where m actually increases slightly as the current density increases. In that case, power law with exponent different from two in experimental data is explained. A series of theoretical J-V data with consideration to high field effect is generated to test conventional parameter extraction method. The parameter is observed to have an error of 25%~40%. The other parameter is quite accurate while the exponent is lower than 3. Furthermore, a new parameter extraction method based on our new model is proposed, and the accuracy of extracted parameters from theoretical data can reach 99.99%. Compared with conventional model, our new model has a better agreement between theory and experiment. By comparing J-V data from different experiments, is found to have dominate effect for J-V with larger exponent at high current density region. On the other hand, for J-V with larger exponent at high current density region, is found to have dominate effect. By the new parameter extraction method, the effects of dissolvent, concentration and time on and were analyzed.