合成聚醚段鏈高分子及應用於染敏太陽能電池之
光電極及電解質

本文分為兩部分。第一部分為合成新穎性高分子分散劑應用於染料敏化太陽能工作電極，第二部分為多孔性彈性體於電解液之應用於染料敏化太陽能電池。第一部分，本研究合成新穎性高分子分散劑(poly(oxyethylene)–segmented imide, POEM)分散二氧化鈦奈米粒子製備具有功能性之薄膜。此功能性高分子(POEM)組成是由聚氧乙烯(oligo(oxyethylene))共軛乙醯胺(imide)主鏈其末端帶有醯胺(amine)官能基與二氧化鈦奈米粒子混摻可以控制薄膜中二氧化鈦粒子和孔洞大小分佈，將此薄膜應用在染料敏化太陽能電池(DSSC)的工作電極研究中。其二氧化鈦薄膜表面粗糙度和形態均可被控制並且利用穿透室電子顯微鏡(Transmission electron microscope, TEM)、掃描式電子顯微鏡(Scanning electron microscope, SEM)和X光繞射儀(X–ray diffraction, XRD)。其二氧化鈦薄膜更近一步應用在DSSC的工作電極與染料具有良好的吸附作用進而提昇高效能，除此之外兼具光散色的特性。在效能表現上，標準光源100 mW cm–2的照射試驗下，可以得到短路電流密度(Jsc)與光電轉換效率(η)分別為18.90 ± 0.15 mA cm–2 和 8.69 ± 0.37%。此效能優越於傳統二氧化鈦利用聚乙二醇(polyethylene glycol, PEG) 所製備之工作電極應用於DSSC在標準光源100 mW cm–2的照射試驗下，其 Jsc與η分別為16.60 ± 0.15 mA cm–2和 7.34 ± 0.02%。其結果可利用光強度調制光電流分析(intensity modulated photocurrent spectroscopy, IMPS)和光強度調制光電壓分析(intensity modulated photovoltage spectroscopy, IMVS)佐證。其利用POEM所製備之二氧化鈦工作電極相較PEG具有良好的電子傳遞特性，此結果顯示會大幅降低工作電極和電極液中的介面進行電子在結合反應，也見接證明POEM所製備之工作電極於DSSC具有優越的效能表現。第二部分，本研究調控不同比例反應性單體合成出彈性體POEM並發展全新共軛高分子(poly(oxyethylene)–segmented amide–imide copolymers, POE–PAI)。此外POE–PAI利用傅立葉轉換紅外線光譜儀(Fourier Transform Infrared Spectroscope, FT–IR)證實具有聚氧乙烯主鏈、胺基酸、醯胺、乙醯胺和分子間醯胺鍵之多功能性官能基使其POE–PAI具有吸收液態電解液之特性並從電子顯微鏡觀察出POE–PAI經由吸收後可產生三維度奈米孔道。此新穎性結構可組成高分子膠態電解液(PGE)應用於DSSC之電解液中。在效能表現上，若PGE含有76%液態電解液可以得到η為9.50 %大幅超越傳統液態電解液η為8.53 %，主要是提升Jsc至19.60 mAcm‒2, 開環電壓(Voc) 至0.76 V。此卓越效能主因為膠態DSSC具有高的導離度和抑制逆反應電子傳遞，可利用光電流轉換效率測量儀(Incident-photo-to-current efficiency, IPCE)、電化學阻抗分析儀(electrochemical impedance spectroscopy, EIS)和暗電流分析佐證而得知。

關鍵字

染料敏化太陽能電池；分散劑；工作電極；聚乙醯胺；高分子膠態電解液；半固態

並列摘要

The thesis consists of two parts, the synthesis of a novel series of polymers and their applications in dye-sensitized solar cell (DSSC). The studies include the dispersion of titanium dioxide for photoanodes and a new design of polymer gel electrolytes with 3D channel nanostructure. The homemade polymeric dispersant, poly(oxyethylene)–segmented imide (POEM), was prepared and proven to be effective for mediating TiO2 nanoparticles to generate the functional film. The presence of the POEM copolymer consisting of oligo(oxyethylene) segments, imide linkages and amine termini in the structure may facilitate the control of TiO2 particle size and film matrix pore size distribution that ultimately promotes the efficiency of the photoanode in DSSC. The surface roughness and morphology of the TiO2 films can be controlled by the POEM presence and characterized by TEM, SEM and X–ray diffraction. The film was further fabricated into a photoanode for DSSC and the interaction with the dye molecules leading to a high performance was evaluated. In addition, the control of light-scattering property of TiO2 photoanode film was obtained by using POEM. The short–circuit current density (Jsc) and power–conversion efficiency (η) at the values of 18.90 ± 0.15 mA cm–2 and 8.69 ± 0.37%, respectively, were demonstrated. The performance is superior to that with the conventional TiO2/PEG photoanode at JSC = 16.60 ± 0.15 mA cm–2 and η = 7.34 ± 0.02%. The measurements are confirmed by analyzing the intensity modulated photocurrent spectroscopy (IMPS) and intensity modulated photovoltage spectroscopy (IMVS). The DSSC of TiO2/POEM also showed a superior electron transit property to the PEG counterpart. It appears that the electron transit is enhanced in the photoanode due to the decrease in recombination at the photoanode/electrolyte interface. Further, the control of the monomer molar ratio in synthesizing the POEM allows to prepare a new class of poly(oxyethylene)–segmented amide–imide copolymers (POE–PAI) or the POEM analogues. The POE–PAI structure possessing multiple functionalities, such as oligo(oxyethylene) segment, amino–acids, amines, imide, and intermolecular linked amides, has been characterized by Fourier Transform Infrared Spectroscope. The gel–like copolymer was capable of adsorbing liquid electrolyte (0.5M LiI, 0.05M I2, 0.5M 4–tert–butylpyridine in 3–methoxypropionitrile) to generate a 3D interconnected nanochannel network, revealed by field emission scanning electronic microscope. This novel structure was used as a matrix in preparing polymer gel electrolyte (PGE) for DSSC that demonstrated a high photovoltaic performance. In particular, the PGE comprising of 76 wt% liquid electrolytes facilitated the cell efficiency up to 9.50 %, significantly superior to the conventional liquid–state cell of 8.53 %, under the conditions of Jsc at 19.60 mAcm–2, open–circuit voltage (Voc) of 0.76 V, fill factor of 0.64. The outstanding performances of gel–state DSSC were ascribed from high ionic conductivity and the suppression of the back electron transfer. Incident–photo–to–current efficiency (IPCE), electrochemical impedance spectroscopy (EIS) and dark current analysis were used to substantiate the results.