分支狀聚酯型高分子分散劑之合成及其於二氧化鈦顏料分散及染料敏化太陽能電池光電極之應用

Synthesis of Branch Poly(oxyalkylene)-Segmented Polyester and Uses for Dispersing Titanium Dioxide and Photoanode of Dye-Sensitized Solar Cells

呂佑安(Yow-An Leu)

指導教授 ： 林江珍

共同指導教授 ： 何國川(Kuo-Chuan Ho)

國立臺灣大學/工學院/高分子科學與工程學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.10549

摘要

本論文主要分為三部分。第一部分為合成分支狀聚酯型高分子分散劑 (命名為PTT)，第二部分為將此高分子分散劑用於二氧化鈦顏料之分散，第三部分則為將此高分子分散劑用於水熱法製備之二氧化鈦奈米粒子分散並應用於製備染料敏化太陽能電池之工作電極。
一系列分支狀聚酯型高分子分散劑之反應物乃使用二元醇、三元醇以及三元酸以3:1:3之莫耳比例進行合成，二元醇之選擇包括不同分子量之聚乙二醇 (分子量為600 g/mol、1000 g/mol、2000 g/mol)、聚丙二醇 (分子量為700 g/mol、1000 g/mol) 或聚乙二醇與聚丙二醇之混合液，三元醇乃使用1,1,1-三羥甲基丙烷作為，三元酸乃使用1,2,4-苯三甲酸酐。此一高分子分散劑主鏈具備可調控之環氧乙烷或環氧丙烷鏈段與酯類官能基、尾端具備羧酸官能基與羥基官能基以及分支狀之分子結構。反應時其官能基與分子量之變化藉用傅里葉轉換紅外光譜(Fourier Transform InfraRed, FT-IR)、酸價(Acid Value)、凝膠滲透層析儀(Gel permeation chromatography, GPC)分析以進行控制 (Chap. 2)。
在二氧化鈦顏料分散的部分，使用聚乙二醇合成所得之含環氧乙烷分支狀聚酯型高分子分散劑作為水相白漿之分散，藉由粒徑分布評估以最佳化漿體之組成並進一步探討分支狀分子結構以及不同環氧乙烷鏈段長短差異對於二氧化鈦顏料分散性之影響(Chap. 3)。此外，亦使用此一含環氧乙烷分支狀聚酯型高分子分散劑於分散水熱法製備之二氧化鈦奈米粒子並將此一所分散之膠體用於製備染料敏化太陽能電池 (Dye-sensitized solar cell, DSSC)之光陽極薄膜，研究發現具備較常之環氧乙烷鏈段分散劑以及其分支狀的分子設計有助於二氧化鈦奈米粒子之分散，使用分散良好之膠體具備較緻密高比表面積之光陽極薄膜以吸附較多的染料以提升最終染料敏化太陽能電池之光電轉換效能 (η) 至8.28% 高於以聚乙二醇分散之二氧化鈦膠體所製得之傳統光陽極(η = 7.18%) (Chap. 4)。二氧化鈦顏料漿體以及二氧化鈦奈米粒子膠體乃藉由動態光散射分析(Dynamic light scattering, DLS).以及穿透式電子顯微鏡(Transmission electron microscope, TEM) 觀察評估其分散性。所製備之二氧化鈦光陽極薄膜進一步使用BET (Brunauer–Emmett–Teller)法、X光繞射儀 (X–ray diffraction, XRD)分析其孔徑分布、比表面積與晶體結構。此外，亦利用電化學交流阻抗分析(Electrochemical impedance spectra, EIS) 、光強度調制光電流分析(intensity modulated photocurrent spectroscopy, IMPS)以及光強度調制光電壓分析(intensity modulated photovoltage spectroscopy, IMVS)分析電子於光陽極之動力學參數。

關鍵字

聚酯 ； 高分子分散劑 ； 黏合劑 ； 二氧化鈦 ； 染料敏化太陽能電池 ； 光陽極

並列摘要

The thesis consists of three parts, the synthesis of a family of poly(oxyalkylene)-segmented ester (designated as PTT), their application in titanium dioxide pigment dispersion, and their application in titanium dioxide nanoparticle dispersion for photoanode of dye-sensitized solar cell (DSSC).
A family of home-made polymeric dispersants, PTT, were synthesized from diol, triol and triacid starting materials with the molar ratio of 3:1:3. Polyalkyene glycols including PEG600, PEG1000, PEG2000, PPG700, PPG1000, PEG1000/PPG1000 were selected as the diols, trimethylolpropane (TMP) as the triol, and trimellitic anhydride (TMA) as the triacid monomers. PTT products contain structure features including ester linkage, tunable weight fraction of poly(oxyalkylene)-segement, hydroxyl and carboxylic acid group termini, and molecular architecture in branched shape. The structures of PTT were characterized by using Fourier-Transformed Infrared Spectrometry (FT-IR), acid value (AV), and gel permeation chromatography (GPC), and the basic properties of the synthesized dispersant were also documented. (Chap. 2)
The PEG derived PTT were further applied in dispersing titanium dioxide pigment in water suspension for white pigment usage. The slurry composition optimization, effect of branching molecular structure and the weight fraction of poly(oxyethylene)-segement of the polymeric dispersant on its pigment dispersibility were discussed (Chap. 3). The PEG derived PTT were also used to homogenize the hydrothermally prepared TiO2 and then fabricated into films of photoanodes in DSSC. The weight fraction of poly(oxyethylene)-segment in the dispersants and the molecular architecture in favoring the branched shape were found to be two predominant factors for the effective dispersion. The ultimate performance of DSSC was measured to be 8.28% for the device efficiency (η) which was significantly higher than the conventional TiO2 photoanode at η = 7.18% (Chap. 4). TiO2 pigment and hydrothermal prepared TiO2 nanoparticles dispersibility was evaluated by dynamic light scattering (DLS) and Transmission Electron Microscopy (TEM) The photoanode film was characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) for surface area and dye loading amount measurement. The kinetics of photo-generated electron in the photoanode including electron life time and electron transit time of the film were studied via electrochemical impedance spectroscopy (EIS), intensity-modulated photocurrent spectroscopy (IMPS) and intensity-modulated photovoltage spectroscopy (IMVS).

並列關鍵字

Polyester ； polymeric dispersant ； binder ； titanium dioxide ； dye-sensitized solar cell ； photoanode

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