染料敏化太陽能電池： 半導體奈米晶體光電極及半固態電解質之研究

Dye-sensitized Solar Cells: Study of Semiconductor Nanocrystal-based Photoanodes and Quasi-solid-state Electrolytes

李權倍(Chuan-Pei Lee)

指導教授 ： 何國川

國立臺灣大學/工學院/化學工程學研究所/博士(2012年)

https://doi.org/10.6342/NTU.2012.01113

摘要

本文主要目的在於提升染料敏化太陽能電池內半導體奈米晶體光電極的電子傳輸以及改善元件的長效穩定性。
在第一章中簡介染料敏化太陽能電池，其中將針對半導體奈米晶體光電極以及半固態染料敏化太陽能電池的歷史背景與應用作完整的回顧。本論文所有研究的實驗部分將整理於第二章。
在第三章，我們添加碳化鈦奈米粒子於光電極的二氧化鈦薄膜中以提升染料敏化太陽能電池的性能。同時，我們發現當碳化鈦在450 °C下燒結，其可部分轉化成具銳鈦礦結構的二氧化鈦晶體。當添加3.0 wt%碳化鈦奈米粒子於光電極的二氧化鈦薄膜，染料敏化太陽能電池的光電轉換效率可由6.61%（純二氧化鈦薄膜光電極）提升至7.56%。碳化鈦能在二氧化鈦薄膜光電極內自轉化成碳化鈦/銳鈦礦二氧化鈦晶體為提升效率的原因。
在第四章，我們使用高性能釕金屬染料CYC-B1（具含長碳鏈之噻吩基團）製備全氧化鋅為主的染料敏化太陽能電池，其光電轉換效率可達4.88%。同時，我們合成均勻且粒子徑為300nm的Polymethylmethacrylate (PMMA)高分子球，將其用來修飾氧化鋅薄膜並組裝於光電極中氧化鋅穿透層之上，作為具微奈米孔徑之光散射層；使用雙層結構之氧化鋅光電極於此系統中，光電轉換效率可進一步提升至5.42%。此效率為使用釕金屬染料且全氧化鋅為主的染料敏化太陽能電池之最高效能值。
在第五章，我們在高分子膠態電解質中添加氮化鈦或氮化鈦/二氧化鈦奈米晶體，並探討此電解質系統對於半固態染料敏化太陽能電池性能影響。當添加3.0 wt%氮化鈦奈米粒子於高分子膠態電解質中，染料敏化太陽能電池的光電轉換效率可由4.15%（純高分子膠態電解質）提升至5.33%。同時，我們發現當氮化鈦在高溫熱處理後，其可部分轉化成具銳鈦礦以及金紅石結構的二氧化鈦晶體。將3.0 wt%氮化鈦/二氧化鈦奈米晶體於添加於高分子膠態電解質中，光電轉換效率可進一步提升至5.68%並具有一千小時不衰退之長效穩定性。
在第六章，我們使用室溫型離子液體1-propyl-3-methylimidazolium iodide (PMII)以及polyaniline-loaded carbon black (PACB)奈米粒子製備不含碘分子的複合電解質並且應用於半固態染料敏化太陽能電池。其最佳光電轉化效率可達到5.81%且此半固態染料敏化太陽能電池在70°C高溫環境下具有一千小時無衰退之優異穩定性。
在第七章，我們主要利用離子液體晶體1-ethyl-3-methylimidazolium iodide (EMII)作為全固態染料敏化太陽能電池的電荷傳輸介質，光電轉化效率值可達0.41%。藉由添加適量的單壁奈米碳管(SWCNT)於EMII中，其效率值可提昇至1.88%。為了進一步提升此系統的元件效能，我們在SWCNT-EMII複合電解質中添加室溫型離子液體PMII同時作為結晶抑制劑以及電荷傳輸介質。全固態染料敏化太陽能電池使用SWCNT-EMII/PMII複合電解質，光電轉化效率可達3.49%。由一千小時長效穩定性測試結果發現，此系統的全固態電解質具有無衰退之穩定性。

關鍵字

染料敏化太陽能電池 ； 離子液體 ； 碳化鈦 ； 碳化氮 ； 長效穩定性 ； 氧化鋅

並列摘要

In this dissertation, the main purposes are to enhance the charge transport in the semiconductor nanocrystal-based photoanodes, and improve the long-term stability of the dye-sensitized solar cells (DSSCs).
In chapter 1, we make a short introduce of DSSCs, and also the completed introductions for semiconductor nanocrystal-based photoanodes of DSSCs and quasi-solid-state DSSCs (QSS-DSSCs). Their history and applications are also discussed here. The experimental section for all of our studies is shown in chapter 2.
In chapter 3, we try to enhance the performance of a DSSC with the incorporation of titanium carbide (TiC) in the titania (TiO2) matrix. It is established that TiC was partially converted into anatase TiO2 when the TiC was sintered at 450 °C. With the incorporation of 3.0 wt% of the TiC in the TiO2 film, the solar-to-electricity conversion efficiency (η) of the cell reached to 7.56% from its value of 6.61% with a bare TiO2 film. “In situ” incorporation of this TiC/anatase TiO2 composite in the commercial TiO2 is considered as the basis for enhanced cell efficiency of the benefited cell.
In chapter 4, a highly efficient ruthenium dye with an alkyl bithiophene group, designated as CYC-B1, is employed as the photosensitizer for a zinc oxide (ZnO)-based DSSC. The DSSC with a ZnO film (designated as ZN20) sensitized with this dye exhibited an η of 4.88%. Further, PMMA spheres with uniform sizes of ca. 300 nm are synthesized and incorporated to template the ZN20 film (designated as PMMA-ZN20); this PMMA-ZN20 film is used as an overlayer on the underlayer ZN20 film to make the photoanode film (ZN20/PMMA-ZN20) of a DSSC; the thus fabricated DSSC shows an η of 5.42%. This efficiency (5.42%) is highest ever for an all ZnO-based DSSC with a ruthenium-based photosensitizer.
In chapter 5, we study on the favorable effects of titanium nitride (TiN) or its thermally-treated version in a polymer-gelled electrolyte for a QSS-DSSC. With an addition of 3 wt% TiN, the η of the DSSC reaches 5.33% from 4.15% of the cell without TiN. X-ray diffraction (XRD) spectra of thermally treated-TiN (tt-TiN) clearly shows the partial conversion of TiN into TiO2 with both anatase and rutile crystal phases. The DSSC with the incorporation of 3 wt% of tt-TiN into its electrolyte shows a further improved η of 5.68%, with reference to the η of TiN-incorporated DSSC. The cell with 3 wt% of tt-TiN also shows unfailing at-rest stability after more than 1,000 h.
In chapter 6, we fabricate a QSS-DSSC by using a room-temperature ionic liquid (IL), 1-propyl-3-methylimidazolium iodide (PMII), and polyaniline-loaded carbon black (PACB) as the composite electrolyte without the addition of iodine. The η of 5.81% is achieved with this type of DSSC. At-rest durability of the QSS-DSSC with PMII/PACB composite electrolyte was studied at 70 °C and shows unfailing durability.
In chapter 7, a solid IL crystal, 1-ethyl-3-methylimidazolium iodide (EMII), employed as a charge transfer intermediate (CTI) to fabricate an all-solid-state DSSC. In addition, single-walled carbon nanotubes (SWCNTs) were incorporated into EMII and achieved a higher η of 1.88%, as compared to that containing bare EMII (0.41%). Moreover, PMII, which acts simultaneously as a co-CTI and crystal growth inhibitor, was used to further improve η. The highest η (3.49%) is achieved using a hybrid SWCNT-binary CTI (EMII/PMII) and shows a durability of greater than 1,000 h.

並列關鍵字

Dye-sensitized solar cells ； Ionic liquid ； Titanium carbide ； Titanium nitride ； Long-term stability ； Zinc oxide

參考文獻

1. Armaroli, N.; Balzani, V., The Future of Energy Supply: Challenges and Opportunities. Angewandte Chemie International Edition 2007, 46, 52-66.

2. Gust, D.; Moore, T. A.; Moore, A. L., Solar fuels via artificial photosynthesis. Accounts of Chemical Research 2009, 42, 1890-1898.

3. Nocera, D. G., Chemistry of personalized solar energy. Inorganic Chemistry 2009, 48, 10001-10017.

4. Grätzel, M., Photoelectrochemical cells. Nature 2001, 414, 338-344.

5. O'Regan, B.; Grätzel, M., A low-cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films. Nature 1991, 353, 737-740.