DSSC中光陽極奈米二氧化鈦管之製備及電子傳輸特性分析

Preparation of TiO2 nanotubes as photoanode in DSSC and analysis of electron transport properties

梁仕昇(Shi-sheng Liang)

指導教授 ： 張合

國立臺北科技大學/機電學院/機電整合研究所/碩士(2011年)

摘要

本論文主要是對於染料敏化太陽能電池（Dye-Sensitized Solar Cells）光陽極薄膜與陽極處理之製備方法、結構與特性分析、電化學阻抗(EIS)探討。以陽極處理法在鈦板上製備出內管徑176.4nm、厚度20nm及長度為17.08μm且具穩定性高、管徑一致性及高純度的陣列式二氧化鈦奈米管，以作為背向光照射與正向光照射光陽極的薄膜。光陽極均需經由450 °C 之煅燒處理，以改善薄膜之緻密性。此外，電解液採用以I-/I3-體系之液態電解液，染料則使用釕錯合物N719染料；而對電極薄膜則以濺鍍法在FTO 玻璃上塗佈一層25 nm 之Pt薄膜。最後，將各電極如三明治方式組裝，來完成敏化染料太陽能電池之製備。接著檢測此DSSC的短路電流、開路電壓、填充因子、IPCE(入射光子-電子轉換效率)及光電轉換效率，並以進一步以電化學阻抗及奈氏圖分析各個元件之間的電子傳輸特性，包括電子再結合速率常數、電子壽命、電子再結合的電荷傳導電阻、有效電子擴散係數、電子在TiO2中的傳導電阻以及電子擴散長度等，並進一步分析多層光陽極與電解質、對電極之電子傳輸特性及關連性，以及對光電轉換效率的影響。
結果顯示以背向照光之陽極處理法製備二氧化鈦管最佳製程參數為NH4F 0.75 wt% + DI 1 wt% + EG 99 wt% 陽極處理反應5小時之二氧化鈦管的管長為17.08μm，管內徑為176.4nm，而單層光陽極之光電轉換效率η(%)為0.841％、有效電子擴散係數 Deff (effective electron diffusion coefficient)為2.30×10-5(cm2/s)、電子擴散長度 Ln (electron diffusion length)為53.44(μm)。
以背向照光之雙層光陽極(AOTnt- TiO2 film)與單層光陽極(AOTnt film)的有效電子擴散係數Deff值，其值為8.25×10-5 cm2/s、4.13×10-5 cm2/s，電子擴散長度Ln 值，分別為62.54 μm、33.23μm，光電轉換效率η(%)分別為1.44%、0.70%，其厚度(LF)分別為37.0μm、17.08 μm。
以正向照光之三層光陽極(AOTnt-Tnt550-TiO2/SWCNT film)染料敏化太陽能電池之光電轉換效率η(%)為5.42%，比起雙層光陽極(AOTnt-Tnt550 film)為4.97%、單層光陽極(AOTnt film)為1.17%之光電轉換效率η(%)較高。電子擴散係數 Deff (effective electron diffusion coefficient)，其值分別為5.86×10-5 cm2/s、1.03×10-5 cm2/s、4.39×10-8 cm2/s。電子擴散長度Ln (electron diffusion length)，分別為58.1μm、22.2μm、1.44μm，其厚度(LF)分別為50.1μm、19.8 μm、1.02 μm。

關鍵字

二氧化鈦管 ； 陽極處理法 ； 電化學阻抗分析 ； 奈氏圖

並列摘要

This study uses highly ordered anatase TiO2 nanotubes (AOTnt) as thin film photoanodes for dye-sensitized solar cells (DSSCs). The high purity nanotube array is prepared by anodization method on a Titanium plate of backlight、directlight photoanode. The inner tube diameter of TiO2 nanotube array inside diameter is 176.4nm, thickness is 20nm and length is 17.08μm. It is high stability, diameter consistency and high photocatalytic. This photoanode need to calcine to 450°C, then the dense of the thin film can be improved.The I-/I3- liquid electrolyte system is used for the electrolyte. The ruthenium polypyridyl complex N719 is used for the dye. The Pt electrode thin film is coated on FTO glass by sputtering and the thickness is 25 nm. Finally, each electrode is assembled by sandwich method to complete the preparation of DSSC. Then, the short circuit current, open-circuit voltage, fill factor, incident photon conversion efficiency (IPCE) and electron transport properties in DSSC are detected. The electron transport properties of each component are analyzed by electrochemical impedance spectroscopy (EIS) and nyquist diagram. The electron transport properties are reaction rate constant for recombination, lifetime of electrons, charge-transfer resistance related to recombination of electron, effective electron diffusion coefficient, effective electron diffusion coefficient, electron transport resistance in TiO2 and electron diffusion length. Each photoanode and counter electrode are analyzed for electron transport properties, interrelation and the effect of electron transport properties. Finally, after the assembling of backlight DSSCs, η=0.841％、Deff = 2.30×10-5(cm2/s)、 Ln = 53.44(μm).
Results show that the backlight photoelectric conversion efficiency of DSSCs in the double-layer photoanodes (AOTnt-TiO2 film) is 1.44%, being higher than the photoelectric conversion efficiency 0.70% of DSSCs of the single layer photoanodes (AOTnt film). The double-layer photoanodes (AOTnt-TiO2 film) have the best effective electron diffusion coefficient, with a value of 8.25×10-5 cm2/s. The double-layer photoanodes (AOTnt-TiO2 film) have more effective electron diffusion coefficient and electron diffusion length than other samples.We further analyze the electron diffusion lengths of the double-layer photoanodes (AOTnt-TiO2 film), single-layer photoanodes (AOTnt film), and single layer photoanodes (TiO2 film), which are 62.54 μm、33.23μm respectively.
Results show that the directlight photoelectric conversion efficiency of DSSCs in the three-layer photoanodes (AOTnt-TiO2-TiO2/SWCNT film) is 5.42%, being higher than the photoelectric conversion efficiency 4.96% of DSSCs of the double-layer photoanodes (AOTnt-TiO2 film) and the photoelectric conversion efficiency 1.17% of DSSC of the single-layer photoanodes (AOTnt film). The three-layer photoanodes (AOTnt-TiO2-TiO2/SWCNT film) have the best effective electron diffusion coefficient, with a value of 5.86×10-5 cm2/s. The three-layer photoanodes (AOTnt-TiO2 film) have more effective electron diffusion coefficient and electron diffusion length than other samples.We further analyze the electron diffusion lengths of the three-layer photoanodes (AOTnt-TiO2-TiO2/SWCNT film), double-layer photoanodes (AOTnt-TiO2 film), and single-layer photoanodes (AOTnt film), which are 58.1μm、22.2μm、1.44μm respectively.

並列關鍵字

Tnt ； Anodization method ； Electrochemical impedance spectroscopy ； Nyquist diagram.

參考文獻

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