| Organic light emitting diodes (OLED) have many adavantages, such as low diven voltage, low cost, high brightness and rapid respond time, which are regarded as next generation ideal display technology. Surrounding this international hot spot in scientific and technical research field, the thesis has focused on studying the surfacial effects and the related characteristics of OLED. By theoretical simulation and experimental work, the methods and characteristics on interfacial effects and interfacial modification have been studied and some innovative results have been achieved. Main contents of the thesis are summarized as follows:1. Considering the influences of dipole layer on the interfacial energy and leakage current, a theoretical model has been introduced with buffer layers. Furthmore, the surfacial morphology, interfacial energy level and luminescence of the device with LiF buffer layer have been studied experimentally. The theoretical results are in agreement with the experimental ones.2. By simplified model, the characteristics of bilayer organic light-emitting diodes have been investigated systematically. Based on the assumptions on carrier concentration, two parameters, the characteristic length of the spatial distribution of charge and effective mobility have been introduced. The characteristics of carriers, electrical strength and I-V have been discussed. Moreover, a simple analytic model with reduced parameters has been presented for the total cell current in bilayer light-emitting diodes with ohmic contacts. Results are in good agreement with both existing experimental data and numerical simulations. This model permits the semiquantitative analyses of the influence of the most important parameters on the EL and cell currents. It is found this model can reasonably elucidates the influence of some material parameters on the recombination current density and provides the methods to optimize the structure and to select suitable electroluminescent materials.3. A conducting polymer polydimethylsiloxane (PDMS) has been studied for the high performance electrode of organic electroluminescence devices. A method to prepare the electrode, consisting of SiC thin film and PDMS, has been investigated. By using ultra thin SiC films with different thickness, the organic electroluminescence devices were obtained in a ultra vacuum system with the model device PDMS/SiC/PPV/Alq3. The measurement shows that the work function of PDMS/SiC anode with a 2.5 nm SiC over layer can be increased by as much as 0.28eV, compared to the conventional ITO anode. The result was attributed to the charge transfer effect and ohmic contacts at the interface.4. A novel device using a diamond-like carbon film between MEH-PPV and aluminum (Al) cathode has been prepared. Diamond-like carbon (DLC) film is deposited as an electron injection layer in organic electroluminescence devices (OLEDs) by radio frequency plasma deposition system. The source material of DLC was n-butylamine. The DLC film thinner than 1.0 nm leads to higher turn-on voltage and decreased electroluminescent (EL) efficiency and a 5.0 nm DLC film significantly enhances the electron injection and results in lowest turn-on voltage and highest EL efficiency. The DLC film exceeding 5.0 nm results in a poor performances of the devices,and EL emission could hardly be detected when the film exceeded 10.0 nm. In addition, the properties of ITO / MEH-PPV/DLC/ Al and ITO / MEH-PPV/LiF/ Al have been studied comparatively.5. Considering the electroluminescence delay after introducing LiF buffer layer, a bilayer OLED theorectical model has been founded. The relations between applied bias, injection barrier, interfical barrier, anode thickness, LiF thickness and electroluminescence delay have been analysed. All the mentioned factors influence the electroluminescence delay. It is proved theorectically that the Ag/LiF cathode with 3.0 nm LiF has the shortest delay response, which is consistent with the experiments.
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