Engineering Functional Interfaces in Organic Light-Emitting Devices
Date Issued
2005
Date
2005
Author(s)
Chen, Chieh-Wei
DOI
en-US
Abstract
Organic light-emitting devices (OLEDs) have been the subjects of intense investigation in recent years due to their applications in efficient, large-area and full-color displays. In OLEDs, characteristics of various interfaces are critical to device performances. This thesis studies structures and characteristics of various interfaces in OLEDs.
By employing the interdiffusion between organic layers, we demonstrated the two-color reconfigurable, three-color reconfigurable, and fuzzy-junction OLEDs. In reconfigurable OLEDs, emission colors and device configurations could be altered after fabrication. The technique for fine patterning of color pixels through thermal imaging of such reconfigurable devices is also established. The fuzzy-junction OLEDs exhibit lower driving voltage and higher efficiency compared to conventional heterojunction OLEDs. High power efficiency (~20 lm/W) is observed in green fluorescent fuzzy-junction OLEDs.
Effective structures of bottom electrodes, one anode structure and one cathode structure, are developed for top-emitting OLEDs. The uv-ozone treated Ag electrode was found to be an effective reflective anode structure for top-emitting OLEDs. The top-emitting devices with such surface-treated Ag anode show device characteristics competitive with those of a bottom-emitting device using the indium tin oxide anode. On the other hand, we developed a highly reflective bottom cathode for inverted top-emitting OLEDs. In such a cathode scheme, the ultrathin Alq-LiF-Al trilayer was used as an effective composite electron-injection layer for the Ag or Al bottom cathode in the inverted top-emitting OLEDs, involving no reactive metals during fabrication. Efficient inverted top-emitting OLEDs employing such a cathode scheme have been demonstrated.
We also proposed a new connecting structure for tandem OLEDs without using reactive metals. With a middle metal layer sandwiched between electron- and hole-injection layers, the connecting structure substantially enhances the characteristics and operational stability of tandem devices. A model of the connecting structure in the tandem devices is proposed and the model is also consistent with the results of the photovoltaic measurements in the tandem OLEDs.
Subjects
有機發光元件
介面
OLED
interface
SDGs
Type
thesis
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