Highly Efficient Solid-State Yellow Light-Emitting Electrochemical Cells
| Autor: | Lo, Chieh-Liang, 羅价良 |
|---|---|
| Rok vydání: | 2019 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 108 In recent years, organic light-emitting diodes (OLEDs) have been widely studied for lighting and display applications due to their high contrast, wide viewing angle and low power consumption. Solid-state light-emitting electrochemical cells (LECs) based on ionic transition-metal complexes (iTMCs) have lower operating voltage than typical small-molecule OLEDs due to electrochemical doping. In addition, the solution-processable LECs have the potential in large-area displays. This thesis will be divided into three parts in optimizing electroluminescence (EL) efficiency of the LECs based on the yellow-emitting ionic iridium complex [Ir(bppz)2(BPhen)]+(PF6-), where bppz is Butylphenylpyrazole and BPhen is 4,7-Diphenyl-1,10-phenanthroline. Firstly, the device thickness is optimized to reach the highest device efficiency. The peak external quantum efficiency (EQE) and power efficiency is 13% and 34.3 lm/W, respectively. Secondly, the blue-emitting ionic iridium complex [Ir(dfppz)2(dmbpy)]+(PF6-), where dfppz is 1-(2′,4′-difluorophenyl)pyrazole and dmbpy is 4,4'-dimethyl-2,2'-bipyridine, is used for the host material for doping of the guest complex [Ir(bppz)2(BPhen)]+(PF6-). By adjusting the doping concentration, the highest EQE and power efficiency of 16.6% and 56.2 lm/W, respectively, can be obtained in the optimized host-guest LECs. Thirdly, a composite substrate containing an embedded diffusion layer is utilized to further improve the device efficiency of the optimized host-guest LECs. With the diffusive substrate, the peak EQE and power efficiency can be further enhanced to 23.7% and 81.2 lm/W, respectively. Furthermore, the EL spectrum becomes more stable since the microcavity effect in the control device without a diffusive substrate can be destroyed in the LEC with a diffusive substrate. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
| Externí odkaz: |
|