Preparation And Properties Of Polymer Light-emitting Devices

Polymer light-emitting diodes (PLED) have attracted much interest due to their potential application. However, some problems, for instance, low efficiency and poor stability, still remain to be solved. Basic research work aiming at these problems has been reported in this dissertation, especially on the research of fabrication. The chief results and conclusion thus arrived at are as folloes:(1) The morphology and electrical properties of indium-tin-oxide (ITO) films which were treated respectively by ethanol, NaOH, sulfuric and oxygen plasma, were studied from microscopic view by atomic force microscopy, X-ray photoelectron spectroscopy and goniometer. It is found that ITO surface roughness decreased after oxygen plasma treatment, which can improve its wetting performance and consequently improve the film performance. On the other hand, oxygen plasma treatment makes ITO film oxidized further, which decreases the number of oxygen vacancy and Sn⁴⁺. This could increase the work function of ITO, which would decrease the device threshold voltage and increase the luminescence efficiency consequently.(2) The morphology and electrical properties of MEH-PPV films were studied by atomic force microscopy, X-ray photoelectron spectroscopy. It is found that technics of fabrication affect the devices'performance. Heat treatment and anneal can improve films'surface, increase function between film and electrode and optimize devices'performance. Otherwise, the change of rev can cause the increase or decrease of films'thickness. It was found that the chance of rev and thickness is reverse by measuring and analyzing from J-V characteristics.(3) Based on a spinning polymer layer of poly(N-vinylcarbazole) (PVK) as hole transport layer (HTL) and an evaporated layer of tris (8-hydroxy)quinoline aluminum (Alq3) as electron transport layer (ETL) and emissive layer (EL), polymer light-emitting diodes (PLEDs) with the structure of ITO/PVK(0⁶0 nm)/Alq₃(60 nm)/ Mg:Ag/Al were fabricated. By measuring and analyzing the Current-voltage- brightness (J-V-B) characteristics, influences of the thickness of HTL on devices...