Interface Modification of Polymer Light Emitting Diodes

• Main Authors: Huang Ming Yi, 黃明義
• Other Authors: R. S. Liu
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/65167732514559194181

碩士 === 國立臺灣大學 === 化學研究所 === 90 === Recently, organic light emitting diodes (OLEDs) play an important role in display technology field because they have a lot of advantages, such as self-luminescence, low electricity consuming, widely viewing angle, fast response time, and high contrast. Most researches are to develop new luminescent materials. However, little researches are to study the problems of the interface. It is said that there are some kinds of energy gap between the indium tin oxide (ITO) (or metal electrode) and conjugate polymer layer. Existing energy gap causes the low luminescent efficiency of present OLEDs. Therefore developing a new technology to improve the properties of the interface is an important target in OLED’s research. In our research, the silane compounds as an organic-inorganic hybrid materials are chosen to improve the properties of the interface between the ITO substrate and main luminescent layer. The silane compounds replace the hydroxyl groups (-OH) adsorbed on the ITO substrate forming a siloxane bond between the Si on one end of the silane compound and an oxygen atom on the ITO surface. The other end of silane compounds have amino, epoxy or phenyl function groups which will bond with the organic main luminescent layer. Nuclear magnetic resonance spectrometer (NMR), ultraviolet/visible absorption spectrometer (UV/VIS), atomic force microscope (AFM), fluorescence spectrometer and luminescent meter are used to study the properties of the interface. We found that N-Phenylaminopropyl trimethoxysilane among the silane compounds can improve the properties of the interface between the ITO and main luminescent layer which leads to promote the luminescent efficiency. Moreover, we use poly(3,4-ethylenedioxy-thiophene) (PEDOT) as the interface between the ITO and main luminescent layer, and follow a special procedure to make the device (PVK+PBD+C6) change its radiative color from green to blue via heat treatment. Furthermore, radiative colors of the devices can be shifted from green to blue and then blue white by applying voltage. Such variation of the colors are strongly correlated with the formation of exciplex within the interface. Based on the results of our research, we can understand that the interface between ITO and main luminescent layer plays a crucial role to promote the luminescent efficiency in OLEDs.