| Summary: | 碩士 === 國立清華大學 === 材料科學工程學系 === 91 === We present the results of a study on how the spin-coating conditions affects the thickness and morphology of polymer thin films, which in turn influence the performance of polymer light- emitting diode (PLED). The poly(2-methoxy-5(-2’-ethylhexyloxy)-1,4-phenylene vinylene) (MEH-PPV) was dissolved in tetrahydrofuran (THF) to form a solution which was then spin-coated to form polymer thin films in the light-emitting diodes. The surface topography of polymeric thin films was observed by using the contact-mode atomic force microscope (AFM). The relationship between spin speed, solution concentration and the device’s electroluminescence behavior was studied. The results showed that the thickness and topography of MEH-PPV thin films strongly influence the electrical properties and electroluminescent performances. Respectively, at constant solution concentration (1.2 %(w/v)) and the highest spin speed (12000 rpm); constant spin speed (1500 rpm) and the lowest solution concentration (0.6 %(w/v)), the best light-emitting brightness was obtained when the thinnest thickness and lowest average roughness (Ra.) were also observed. On the other hand, we also present the influence of dusty particles, oxygen and water vapor existing in open-public air to opto-electrical properties, performance, operating time and degradation mechanism of PLED by using nitrogen glove bag and cathode protective layer in preparation and operation processes of devices. It can be found that the electrical property and electroluminescent brightness of the diode prepared in nitrogen glove bag are better than it prepared in open-public air; besides, the operating time of the diode covered with a cathode protective layer is longer than it exposed to open-public air. According to our many experimental evidences, we can verify unequivocally that dusty particles, oxygen and water vapor existing in open-public air would cause devices degradation being accelerated, such as poor electrical property, performance and short operating time.
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