Investigation of electronic structures and interfacial chemistries of electrodes in organic optoelectric devices via synchrotron radiation induced photoemission spectroscopy
Date Issued
2014
Date
2014
Author(s)
Liao, Guo-Kai
Abstract
In this thesis, we study the methods to improve the effectiveness of electrodes in organic optoelectronic devices, in particular to enhance the efficiency of carrier injection, conductivity and hence the devices performance. In addition, high-resolution synchrotron radiation induced photoelectron spectroscopy was used to study the chemical and physical properties at the device interfaces.
First, we investigate molybdenum trioxide (MoO3) as hole injection layers in hole only devices. The reductions of Mo atoms are more obvious in the devices with thinner MoO3 layers, with more gap states to increase the hole injection path and to enhance the efficiency of injection.
On the other topic, we use graphene as electrodes in organic solar cell devices. We demonstrated the polymer-free transfer method that can transfer large area CVD-graphene to any substrate to reduce surface tension and residual contaminant. The polymer-free transferred graphene films also show good quality and high electrical conductance that make them suitable for conductive electrodes. Furthermore, in order to resolve the carrier injection barrier problem, we use doping process to change the work function of the graphene. It decreases misalignment between the Fermi level of electrodes and the HOMO and LUMO level of carrier transport layers. As a result, it not only enhances the device performance but also increases the conductivity of graphene, which provide more advantages for graphene application in the future.
Subjects
光電子能譜
有機發光二極體
石墨烯
三氧化鉬
同步輻射
Type
thesis
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