臺灣博碩士論文加值系統

理想的色素增感型太陽電池(Dye-sensitized Solar Cells, DSSC)對電極必須具備：(1).良好的導電性以降低串聯電阻，(2).極佳的化學安定性，以避免受到電解液的侵蝕以及參與電化學反應，(3).具有降低媒子(mediator)氧化還原反應之過電壓(over-potential)，提升供給還原電子的速率。(4).高表面積以提升質傳速率。
本研究利用奈米碳管具有快速轉移電子速度、多孔性高表面積及高導電性等特性，因此以其做為DSSC對電極材料。奈米碳管的合成使用常壓熱化學氣相沉積法，以Co-Mo/MgO載體觸媒，C2H2為碳源，H2或NH3為還原氣體，合成的主產物是多壁奈米碳管(multiwalled nanotubes, MWNT)。本法特點是不受基板大小限制、高奈米碳管產率以及容易純化分離等。研究發現本系統適合前處理溫度為800℃，成長溫度為800~900℃密度較高。成長溫度越高奈米碳管管徑越大(7~13 nm)，系統產率為0.733g-CNT/hr，成長速率在成長的前10分鐘為最快，達到0.057g-CNT/min.g-cat。
純化後的MWNT均勻分散在ITO導電面上，製作對電極及組裝DSSC。I-V特性量測證明，CNT對電極擁有較高的開路電壓，VOC=0.65V與短路電流，ISC=3.05 mA，比傳統白金對電極在相同測試條件下相比，VOC=0.49V，ISC=1.86 mA增加不少。相同[KI]/[I2](5:1)，改變電解質濃度發現：電解質濃度與短路電流之間，有一最佳值[KI]/[I2]=0.3M/0.06M，此時VOC=0.65V，ISC=3.05 mA，相同[KI]/[I2]比例可以維持固定的開路電壓，VOC。當固定[KI]=0.3M，改變[I2]，I-V量測結果顯示：增加[I2]，可以提高短路電流。以太陽電池等效電路分析實驗數據，由理想二極體串聯電阻公式得到：上述最佳CNT對電極(ISC=3.05，VOC=0.65V)的等效串聯電阻，Ro=138 Ω，理想因子(ideal factor) n=0.56，而相同情況之白金對電極，=0.4, Ro=190 Ω。證明奈米碳管確實可以改善對電極的電子傳輸特性。

The ideal counter electrodes of Dye-Sensitized Solar Cells(DSSC) must meet the following requirement: (1).Good electrical conductivity to reduce the series resistance (RS), (2).Excellent chemical stability to protect from corrosive electrolytes and take part in undesired electrochemical reactions, (3).To reduce the over-potential of the redox couples (mediator, i.e. I-/I3- in typical DSSC) and (4).High surface area for mass transfer.
Fullerenes family such as C60 and carbon nanotubes(CNTs) have better electron affinity for fast transfer of photocurrent(electron shuttle),. Carbon nanotubes have high porosity, large surface area with good electric conductivity and relatively easy synthesized in lab. Scale. Accordingly, in this study, we had fabricated multiwalled carbon nanotubes(MWNT) based counter electrode of DSSC in endeavor for cell performance improvement. MWNTs were synthesized by atmospheric thermal chemical vapor deposition over Co-Mo/MgO by using C2H2 as carbon source and H2/NH3 as reducing ambient at 700~900oC. The major products were multiwalled carbon nanotubes with diameter around 7~13 nm. The as-synthesized MWNTs with high carbon yield are easily purified and processed. The optimal pretreatment temperature is 800 oC. For higher nanotube density, reaction temperature of 800~900oC is desirable. As the growing temperature is increased, the diameter of MWNT is larger. One of the production yield is 0.733 g-CNT/hr whose growth rate is fastest at the very start of 10min.(0.057 g-CNT/min. g-cat).
After purification of the as-grown MWNTs, finely dispersed CNTs were anchored on the ITO glasses as the counter electrode of DSSC. After fabrication of TiO2 working electrode dyed with mercurochrome. The assembled DSSC was tested for I-V character under illumination. It revealed that CNT-based counter electrode own superior VOC and ISC under identical conditions. In comparison with the traditional Pt-counter electrode(VOC=0.49 V and ISC=1.86 mA), the CNT- counter electrode possessed higher cell performance with VOC=0.65 V and ISC=3.05 mA. After keeping the [KI]/[I2] to 5/1, the influence of different electrolyte concentration were invesitagted. The results shows that there is optimal value of [KI]/[I2]=0.3 M/0.06 M. Under the given electrolyte value, the DSSC have VOC=0.65 V and ISC=3.05 mA. Besides, it shows that under identical [KI]/[I2] ratio, the VOC is always kept the same. By varying the [I2] and keeping [KI]=0.3 M, the ISC will increase as the [I2] is increased. The equivalent solar cells circuit analysis shows that the series resistance under best cell performance in this study is Ro=138 Ω, with ideal factor n=0.56 in comparison to that of Pt-counter electrode with Ro=190 Ω, n=0.4. As a conclusion, the CNTs is effective increase the electron transfer property of counter electrode of DSSC.

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簽名頁
授權頁．．．．．．．．．．．．．．．．．．．．．．．．．．．．iii
中文摘要．．．．．．．．．．．．．．．．．．．．．．．．．．．iv
英文摘要．．．．．．．．．．．．．．．．．．．．．．．．．．．vi
致謝．．．．．．．．．．．．．．．．．．．．．．．．．．．．．vii
目錄．．．．．．．．．．．．．．．．．．．．．．．．．．．．．viii
圖目錄．．．．．．．．．．．．．．．．．．．．．．．．．．．．xiii
表目錄．．．．．．．．．．．．．．．．．．．．．．．．．．．．．xvi

第一章 緒論．．．．．．．．．．．．．．．．．．．．．．．．．．．1
1.1奈米碳管．．．．．．．．．．．．．．．．．．．．．．．．．．．1
1.2奈米碳管的結構特性．．．．．．．．．．．．．．．．．．．．．．5
1.2.1奈米碳管的電性．．．．．．．．．．．．．．．．．．．．．．．5
1.2.2奈米碳管的機械特性．．．．．．．．．．．．．．．．．．．．．6
1.3奈米碳管的主要製程．．．．．．．．．．．．．．．．．．．．．．7
1.3.1電弧放電法(Electric Arc Discharge)．．．．．．．．．．．8
1.3.2雷射蒸發法(Laser Ablation)．．．．．．．．．．．．．．．．9
1.3.3化學氣相沈積法(Chemical vaper deposition)．．．．．．．10
1.4 奈米碳管的成長機制．．．．．．．．．．．．．．．．．．．．．11
1.5 濕式觸媒．．．．．．．．．．．．．．．．．．．．．．．．．．17
1.6 奈米碳管的純化．．．．．．．．．．．．．．．．．．．．．．．19
1.6.1氧化法．．．．．．．．．．．．．．．．．．．．．．．．．．．19
1.7 奈米碳管的應用．．．．．．．．．．．．．．．．．．．．．．．21
1.7.1 複合材料的應用(Composites)．．．．．．．．．．．．．．．22
1.7.2 儲氫材料的應用(Hydrogen Storage)．．．．．．．．．．．23
1.7.3 掃描探針的應用(probes)．．．．．．．．．．．．．．．．．23
1.7.4 微型感測器(sensor)．．．．．．．．．．．．．．．．．．．24
1.7.5 場發射平面顯示器(Field Emitter for
Flat Panel Display)．．．．．．．．．．．．．．．．．．25
1.7.6 燃料電池．．．．．．．．．．．．．．．．．．．．．．．．．26
1.7研究動機與背景．．．．．．．．．．．．．．．．．．．．．．．26
第二章CNTs實驗部．．．．．．．．．．．．．．．．．．．．．．．．29
2.1藥品與氣體．．．．．．．．．．．．．．．．．．．．．．．．．．29
2.2反應設備．．．．．．．．．．．．．．．．．．．．．．．．．．．29
2.3觸媒製備．．．．．．．．．．．．．．．．．．．．．．．．．．．31
2.4 奈米碳管合成．．．．．．．．．．．．．．．．．．．．．．．．32
2.5純化．．．．．．．．．．．．．．．．．．．．．．．．．．．．．32
2.6 微結構分析．．．．．．．．．．．．．．．．．．．．．．．．．．33
2.6.1 掃描式電子顯微鏡(Scanning Electron Microscopy; SEM)．33
2.6.2 穿透式電子顯微鏡(Transmission Electron Microscopy;TEM)．34
2.6.3 拉曼光譜儀(Raman spectrnum;RS)．．．．．．．．．．．．．．35
第三章CNTs成長結果與討論．．．．．．．．．．．．．．．．．．．．．37
3.1前言．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．37
3.2 觸媒型態上的觀察．．．．．．．．．．．．．．．．．．．．．．．37
3.3 不同觸媒負載量的表面觀察．．．．．．．．．．．．．．．．．．．39
3.4前處理時間、溫度的影響．．．．．．．．．．．．．．．．．．．．．42
3.4.1前處理時間的影響．．．．．．．．．．．．．．．．．．．．．．．43
3.4.2前處理溫度的影響．．．．．．．．．．．．．．．．．．．．．．．44
3.5成長時間、溫度的影響．．．．．．．．．．．．．．．．．．．．．．46
3.5.1成長溫度的影響．．．．．．．．．．．．．．．．．．．．．．．．47
3.5.2成長時間對碳產率的影響．．．．．．．．．．．．．．．．．．．．49
3.6 純化前後的影響．．．．．．．．．．．．．．．．．．．．．．．．．50
第四章 DSSC對電極之研究．．．．．．．．．．．．．．．．．．．．．．53
4.1 研究背景．．．．．．．．．．．．．．．．．．．．．．．．．．．．53
4.2色素增感型太陽電池(Dye-sensitized solar cells,DSSC)簡介．．．55
4.3 色素增感型太陽電池對電極．．．．．．．．．．．．．．．．．．．．56
4.4光電化學太陽電池．．．．．．．．．．．．．．．．．．．．．．．．．58
4.5 色素增感型電化學電池(DSSC)的優點及其工作原理．．．．．．．．．．62
4.6有機太陽能電池之光電轉換特性．．．．．．．．．．．．．．．．．．．67
4.6.1 短路電流( Isc，short circuit current )．．．．．．．．．．．67
4.6.2 開路電壓 ( Voc，open circuit voltage )．．．．．．．．．．．67
4.6.3 填充因子 ( FF，fill factor )．．．．．．．．．．．．．．．．．68
4.6.4 能量轉換效率 ( η，power conversion efficiency )．．．．．．68
4.7 DSSC實驗部份．．．．．．．．．．．．．．．．．．．．．．．．．．．70
4.7.1 實驗藥品．．．．．．．．．．．．．．．．．．．．．．．．．．．．70
4.8 實驗步驟．．．．．．．．．．．．．．．．．．．．．．．．．．．．．70
4.8.1氧化銦錫玻璃(ITO)基板之清洗．．．．．．．．．．．．．．．．．．．70
4.8.2 工作電極的製作．．．．．．．．．．．．．．．．．．．．．．．．．71
4.8.3 對電極的製作．．．．．．．．．．．．．．．．．．．．．．．．．．72
4.8.4 加入電解液及封裝．．．．．．．．．．．．．．．．．．．．．．．．73
4.9 I-V曲線之充電特性量測．．．．．．．．．．．．．．．．．．．．．．．73
4.10 太陽能電池之串聯電阻．．．．．．．．．．．．．．．．．．．．．．．76
4.11 結果與討論．．．．．．．．．．．．．．．．．．．．．．．．．．．．78
4.11.1 無碳管添加之白金對電極．．．．．．．．．．．．．．．．．．．．．78
4.11.2 添加碳管對DSSC之影響．．．．．．．．．．．．．．．．．．．．．．79
4.11.3 改變不同濃度電解液對DSSC之I-V特性研究．．．．．．．．．．．．．79
4.11.4電解液比例對DSSC之I-V特性研究．．．．．．．．．．．．．．．．．．80
4.11.5 串聯電阻量測計算．．．．．．．．．．．．．．．．．．．．．．．．82
第五章 結果與討論．．．．．．．．．．．．．．．．．．．．．．．．．．．．84
5.1結論．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．84
第六章 參考文獻．．．．．．．．．．．．．．．．．．．．．．．．．．．．．85

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