Polymer Light Emitting Devices : A study on how the electrode-polymer interface affects the performance of polymer light emitting devices
Sammanfattning: The research reported in this thesis is concerned with a new type of semiconductor device that can be realised by using thin films of semiconducting polymers, or conjugated polymers. In this thesis only one family of these conjugated polymers is studied, namely poly-(para-phenylene vinylene) and derivatives thereof.This thesis focuses on how a change in the interface conditions between electrodes and polymer affects the performance of the devices. Especially on how low workfunction metals, e.g. calcium, magnesium interact with poly-(para-phenylene vinylene), and derivatives thereof. Those low workfunction metals are often used as the negative electrode for polymer light emitting devices. This type of light emitting device is described in this thesis and the issues off charge injection and transport is discussed in detail. Also the difference between the ideal theoretical models and real life system is in focus.Studies of different types of degradation mechanisms in the polymer light emitting devices are also included. The degradation of the polymer material due to low energy electrons from the thermal electron beam evaporator during fabrication has been studied in detail. Also included is an investigation and comparison of used and unused polymer light emitting devices that has been done with the help of sputtered depth profile analysis with surface sensitive Auger spectrometry.
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