Bilayer Light-Emitting Electrochemical Cells: Ionic Effects of Solid Polymer Electrolyte
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Authors
Tong, Chaobei
Date
Type
thesis
Language
eng
Keyword
Solid Polymer Electrolyte , Light-emitting Electrochemical Cells , Ion Transport , Electrochemical Doping , Electroluminescence
Alternative Title
Abstract
Polymer light-emitting electrochemical cells (PLECs) are organic solid-state devices that operate on in situ electrochemical doping and the formation of a light-emitting p-n junction. Bilayer LECs consist of a solid polymer electrolyte (SPE) underlayer and a conjugated polymer (CP) top layer. Aluminium electrodes with 2mm gap size were deposited on top of the CP layer and formed a planar configuration. Planar bilayer LECs with large gap sizes brought unique opportunities to visualize the in situ doping propagations with imaging techniques. Separating the CP from the SPE provided the potential to study the SPE layer itself and lead to a better performing light emitting device. In this thesis, four different studies were conducted to explore ionic transportation in the CP, the SPE, and the CP/SPE interface. In the study of salt concentrations in the SPE, the increase in ionic concentrations improved the performance of LECs in terms of doping propagation speed, junction formation time, and cell current. However, a current leveling off was observed at high salt concentrations, while light emitting p-n junction overlaps with the cathode which is undesirable. In the second study, by increasing SPE layer thickness, a significant improvement in device performance was observed, however, no further improvement was observed as the thickness went beyond 500nm. In the study of cationic effects, devices with smaller cation sizes had a higher current and faster doping propagation, whereas devices with large cations require a higher bias voltage and temperature to turn on. The improved performance of bilayer LECs compared to single-layer LECs suggested that interlayer ionic transportation was not the major factor that limited the performance of LECs. In the final chapter, LECs with salt concentrations as low as 0.005 were successfully turned on. For devices with lower salt concentrations, however, no light-emitting p-n junction was formed. These studies demonstrate the importance of ion transport in LEC operation and point to new directions for improving the device performance.
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Queen's University's Thesis/Dissertation Non-Exclusive License for Deposit to QSpace and Library and Archives Canada
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Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.
ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.