Several results were reviewed on the charge injection into thin conjugated polymer films. The space charge limited tunneling current (SCTC) and space-charge limited current (SCLC) models were used to explain the charge injection and transport in conjugated polymer films such as those used in organic light emitting diodes. On the basis of regional approximation, the effect of the space charge on the current density of electrons tunneling from metal electrodes to the lowest unoccupied molecular orbital of a polymer film is calculated. The space charge is considered to decrease with increasing distance of the injecting electrode. If the space charge occupies only a limited region between the tunneling (short) distance and the collecting electrode, the current (I) is found to be independent on a power law of the applied voltage (V). However, if the space charge occupies all the region between the tunneling distance and the collecting electrode, I is found to vary exponentially on V for lower V values, and that follow approximately the law of Child at high V in region I, the law of Trap filled limited current at middle voltage in region II and the region III show Ohm¡¦s law at lower voltage. The space charge limited tunneling current (SCTC) theory gives the same results of the space charge limited conduction theory when the energy barrier for charge carrier injection is small or when the polymer layer is thick.
Under various bias voltages, the charge transport mechanism was analyzed to investigate the effects on the thin conjugated polymer films induced by the parameters such as background concentration, trap-state density and space charge etc... The results show the transport current decrease with increasing the trap-state density and also increase the characteristic temperature parameters.
In this study, the regional approximation is applied to calculate the charge injection and current transport mechanism in the organic thin film. The SCTC and SCLC models are compared to the experimental data. It shows that there is a good agreement between theory and experiment, concerning both current magnitude and current versus voltage dependence. It is very important that our model gave a new way to simplify the calculation and to discuss the charge transport of organic light emitting diode.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0703103-104248 |
| Date | 03 July 2003 |
| Creators | Chiang, Sheng-Ping |
| Contributors | Wan-Chuan Kuo, Cheu-Pyeng Cheng, Uerng-Yih Ueng, Ai-Na Hung, Chih-Hsiung Liao |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0703103-104248 |
| Rights | not_available, Copyright information available at source archive |
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