穩定自由基搭配導電高分子應用於有機電致色變元件

Organic Electrochromic Devices Based on Stable Free Radical (TEMPO) and Conducting Polymers

胡致維(Chih-Wei Hu)

指導教授 ： 何國川

國立臺灣大學/工學院/高分子科學與工程學研究所/博士(2011年)

https://doi.org/10.6342/NTU.2011.02617

摘要

本論文主要探討有機分子2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)當作穩定自由基提供與得到電子，並應用於電致色變元件之中，討論搭配不同電致色變材料以及操作環境下的影響。首先先對電致色變材料與元件的性質與量測方法作一簡短的介紹，並對有機電致色變分子與高分子的合成方法以及TEMPO的歷史與應用端做一完整的介紹。
TEMPO的電化學特性與適用的環境先作一基礎之研究。我們更換了六種不同的有機溶劑以及不同的操作電位，找出TEMPO分子最適合進行氧化還原反應之環境為propylene carbonate (PC)溶劑，搭配最適化之PProDOT-Et2導電高分子電致色變薄膜所組成的元件中，操作在-0.5 ~ 0.9 V之下有著最佳之元件長期穩定性。此種混合式的元件具有著不需搭配薄膜電量之優點，由TEMPO穩定地提供所需要之電子來使用的高分子薄膜能夠完全地著去色，混合式的元件在590 nm波長之下具有著69%的光學穿透度變化。
TEMPO被使用來當作穩定的對電極，搭配兩種不同的還原著色材料：PEDOT以及heptyl viologen (HV)來組裝成一具有多色階之混合式電致色變元件。 根據操作電壓的不同，元件所操作的系統也不同，分成兩個階段：TEMPO-PEDOT系統以及TEMPO-HV系統。當以TEMPO-PEDOT系統運作時，元件可以低電壓取得光學穿透改變約20%在610 nm波長之下；而以較高電壓操作時，元件可取得光學改變高達69%。
TEMPO分子進一步的搭配固態電解質Succinonitrile (SN)以及奈米等級之SiO2顆粒來組成一具有高著色效率的全固態元件。奈米等級之SiO2顆粒不但有消除SN固態電解質之結晶所造成的去色問題，且進一步的提供電子運動的通道，提高HV沈積於ITO玻璃上之效率，進而提高元件的著色效率。
TEMPO被應用來不只當作提供電子之氧化還原對，且可以當作用來接受電子搭配polyaniline (PANI)來使元件可顯現出三種狀態的表現。當元件被操作在正電位時，此時系統是一個TEMPO-HV的表現，呈現出綠色到藍色的狀態；另一方面，當系統被操作在負電位時，系統將呈現一個PANI-TEMPO的狀態，呈現出由綠色到無色的情況。根據以上的結果，TEMPO不只被應用來當作搭配還原著色的材料，且可以搭配氧化著色的材料來使的TEMPO的應用更加的多元化。
在附錄A中介紹了應用TMPD與HV搭配固態電解質SN所形成的全固態電致色變元件，其電流響應與光學反應速度均比溶液態元件性質來的優秀。附錄B則應用了電化學式石英震盪天平(EQCM)儀器，對一氧化著色之電致色變高分子PhSN Diamine-Pas進行不同離子傳輸於高分子薄膜中的運動模式探討，希望找出最適合應用的電解質鹽類系統。

關鍵字

TEMPO ； 穩定自由基 ； 電致色變 ； 導電高分子 ； 混合式電致色變元件 ； 氧化還原對

並列摘要

In this dissertation, the main propose is to investigate the electrochemical properties of the organic molecule 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and its applications for electrochromic devices.
Firstly, we make a short introduce of electrochromic (EC) materials and devices and also a completed introduction of conducting polymers and its’ synthesis methods. The history and applications are discussed here.
A stable organic radical, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), was studied. We employed TEMPO as a cathodic radical provider in propylene carbonate (PC) and poly(3,4-propylenedioxythiophene) derivatives (PProDOT-Et2) as an anodic electrochromic (EC) thin film, which was obtained through electropolymerization. By assembling them together in a device, the electrochemical and optical performances of this hybrid electrochromic device (ECD) showed reversible cycling stability and high absorbance attenuation in the visible range. By selecting proper electrolytes (LiClO4/PC) and controlling the deposited charge of the PProDOT-Et2 thin film, it was possible to obtain a transmittance change (ΔT) of up to 69% at 590 nm with no degradation after operating between -0.5 and 0.9 V for 10,000 cycles.
We talk about TEMPO and two electrochromic (EC) materials, poly(3,4-ethylenedioxythiophene) (PEDOT) and heptyl viologen (HV(BF4)2) were utilized to fabricate a hybrid electrochromic device (ECD). PEDOT and HV(BF4)2 were respectively used as film and solution type cathodic EC materials. The novel ECD exhibited two-stage redox reactions with high absorbance attenuation in the visible region. With the variation of the operating voltage, a transmittance change (ΔT) of 20% at 610 nm was observed in the first stage (-0.5 ~ 0.8 V), and that of 68% was observed in the second stage (0.9 ~ 1.5 V). Furthermore, fast switching times of 6.9 and 2.1s were estimated for bleaching and darkening, respectively. The coloration efficiencies at 610 nm were found to be 171.9 cm2C-1 and 91.0 cm2C-1 for the first and second stages, respectively.
Continuously, heptyl viologen (HV(BF4)2) works as the cathodic coloring solution (electrochromic), TEMPO as the anodic radical provider (ion-storage layer), and crystals of succinonitrile (SN)-plastic as the solid matrix. The electrochemical and electrochromic properties of HV(BF4)2 and TEMPO molecules are analyzed from their in a 0.1 M electrolyte of tetrabutylammonium tetrafluoroborate (TBABF4) in PC. 6 wt% silicon dioxide (SiO2) nanoparticles is added to the matrix to eliminate its crystalline nature. This all-solid-state ECD made with this non-crystalline solid matrix shows a high optical contrast with coloration efficiencies of ca. 65.5 and 342.2 cm2/C at 610 nm at two stages. The transmittance of the ECD at 610 nm has changed from 81% (bleached) to 6% (darkened), with an applied potential of 1.5 V.
A novel hybrid type electrochromic device (ECD) was fabricated, using a stable TEMPO, polyaniline (PANI) and heptyl viologen (HV(BF4)2). PANI and HV(BF4)2 were used as film and solution type anodic and cathodic EC materials, respectively in chapter 6. TEMPO acts only as an ionic storage layer and works in pair with either of the electrochromic materials. With the variation of the operating voltage between 0 ~ 1.5 V the TEMPO-HV system showed electrochromism and a transmittance change (ΔT) of 46% at 550 nm. With the variation of the voltage between 0 ~ -1.0 V the TEMPO-PANI system showed electrochromism and a ΔT of 45% at 700 nm.

並列關鍵字

Conducting polymer ； Electrochromism ； Hybrid type ECD ； Stable free radical ； Redox pair

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