高導電性透明導電高分子之開發與光電元件應用

Development of High-Conductivity Transparent Conducting Polymers and Their Optoelectronic Applications

呂濬洋(Chun-Yang Lu)

指導教授 ： 吳忠幟

國立臺灣大學/電機資訊學院/電子工程學研究所/博士(2015年)

https://doi.org/10.6342/NTU.2015.11012

摘要

透明導體的開發對於高效率有機光電元件的普及應用相當關鍵，然而目前常用的氧化銦錫 (Indium Tin Oxide, ITO)、氟摻雜氧化錫(fluorine-doped tin oxide, FTO)等為主的透明導體，其真空製程複雜且包含昂貴金屬元素，因此需研究替代型之透明導體。本論文以研究高導電性/高透明度/低折射率/自發性奈米結構的導電高分子PEDOT:PSS作為低製程/設備成本、低原料成本及具基板成膜匹配性的透明導體，並有效應用於高效率低成本染料敏化太陽能電池 (Dye Sensitized Solar Cell, DSSC)及高效率有機發光二極體 (Organic Light-Emitting Diode, OLED)。
在DSSC之對電極研究中，運用高極性、高沸點溶劑混合方式輔以堆疊製程獲得具有高導電性、高電化學活性、高PEDOT成份及具有奈米纖維和奈米孔隙結構的導電高分子PEDOT:PSS，可以有效地取代DSSC中需電化學活性的Pt催化電極或需同時具有電化學活性及導電性的Pt/FTO的對電極，在元件效率表現上相當優異。
在OLED之透明電極研究中，組合低折射率的透明電極導電高分子PEDOT:PSS與較水平放光偶極材料(preferential horizonal emitting dipoles)，可有效抑制波導模態(waveguided modes)，同時將發光層位置適當地遠離金屬電極可有效降低表面電漿模態(suppresses surface plasmon modes)，並透過有效外部出光萃取結構可提升總體耦合效率。
結論，藉由對導電高分子PEDOT:PSS光電特性的系統性探討，可提供未來一簡易且效能良好的元件設計於綠能及顯示/照明的應用上。

關鍵字

透明導體 ； 導電高分子 ； PEDOT:PSS ； 染料敏化太陽能電池 ； 有機發光二極體

並列摘要

Transparent conductors are essential for high-efficiency organic optoelectronic. However, there is a need to replace currently widely used ones like indium tin oxide (ITO) and fluorine-doped tin oxide (FTO), due to their high cost. In this thesis, we develop the conducting polymer PEDOT:PSS having high conductivity/high transparency/low refractive index/spontaneous nanostructure as transparent conductors. It could have low fabrication cost, low material cost and better compatibility with substrates, and we successfully apply it to high-efficiency /low-cost dye sensitized solar cells (DSSCs) and high-efficiency organic light-emitting diodes (OLEDs).
First, we focus on its application in counter electrodes of DSSCs, High-conductivity and highly electrochemically active PEDOT:PSS films with nanofibrillar, nanoporpous, and PEDOT-richer surface structures are spontaneously induced by addition of highly polar, high-boiling-point co-solvent and by repeated solution coating. They are useful as an the effective electrocatalytic layer or a dual-function electrocatalytic/conductive layer in Pt-free/FTO-free counter electrodes of DSSCs and have efficiencies similar to those using Pt/FTO-containing counter electrodes.
Second, we focus on its application in transparent electrodes of OLED. Combination of low-index ITO-free transparent electrodes and the preferentially horizontal dipole emitters realized highly efficient phosphorescent OLEDs. Adoption of low-index electrodes in OLEDs, in addition to suppressing waveguided modes, also effectively suppresses surface plasmon modes with larger emitter-to-metal distances yet with better immunity to accompanied increase of competing waveguided modes. Overall coupling efficiencies of OLED internal radiation into substrates are thus substantially enhanced and very high EQEs can be achieved through effective extraction of radiation within substrates.
In conclusion, optoelectronic properties of conducting polymer PEDOT:PSS were systematically investigated and we demonstrated several applications in green energy and display/lighting.

並列關鍵字

transparent conductors ； conducting polymers ； PEDOT:PSS ； dye sensitized solar cells (DSSCs) ； organic light-emitting diodes (OLEDs)

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