臺灣博碩士論文加值系統

太陽能電池因一次能源的耗盡，近年的發展日益快速，並被期待成為未來一項乾淨能源的選擇。從矽基元件到染料敏化元件的進展可說是一項大躍進，使得製作程序單純化及成本大幅降低，有可能成為太陽能電池未來的主流。其中的核心材料以二氧化鈦為代表性，先後發展出不同的被覆製程，卻因必要的後熱處理(約>400℃)及伴隨濕式製程衍生的廢液問題，引發乾式製程的探討動機，本研究嘗試使用乾淨，製程簡單，成本低廉的電弧離子鍍來製備二氧化鈦層，並探討重要的製程參數包括氧氣分壓、基材偏壓、沉積壓力以及沉積時間對微觀結構及其染料敏化元件ITO glass/〔TiO2(N3 dye)〕/ I+LiI electrolyte/Pt/ITO glass之光電轉換效率的影響。
研究結果顯示；較低的氧氣分壓所得鍍膜皆形成不足氧的TiO結構，鍍膜外觀的顏色是較不透光的深藍色並無銳鈦礦相，只有在氧氣分壓大於0.35 Pa的條件下，鍍膜才有銳鈦礦相出現並呈現透明。基材偏壓的施加使得鍍膜外觀亦漸漸變得透明，並隨著基材偏壓上升而更為緻密。沉積壓力提高時，銳鈦礦相逐漸成為鍍膜之主導相結構，而鍍層逐漸疏鬆化，過高的沉積壓力甚且導致鍍膜細晶化。沉積時間的延長，金紅石相漸漸減少並且對應出更大的鍍膜比表面積。雙電弧源的使用提高了鍍膜的成長速率。
綜合鍍膜之微觀組織可得知短路電流會隨著氧氣分壓的提高而上升係因銳鈦礦相含量的逐漸增加所致。基材偏壓對短路電流呈負面影響係鍍膜緻密化損失比表面積所造成。沉積壓力的上升雖有利於生長疏鬆之鍍膜，卻因過高之沉積壓力導致細晶化而再度降低短路電流。沉積時間的延長使膜厚增加進而提高比表面積而有較大的短路電流。在全氧的環境下，無基材偏壓施以60分鐘的鍍膜可得到本研究之最高短路電流0.052 mA/cm2及0.08%的光電轉換效率。雙電弧源的使用在縮短為30分鐘的相同沉積條件下，則可得到近似之結果。
經由上述說明，可知電弧離子鍍所得之二氧化鈦光電轉換效率，鍍膜中之銳鈦礦相含量為必要之條件，並被鍍膜比表面積所主導。在全氧環境、沉積壓力適中、不施加基材偏壓以及足夠的沉積時間下，在低於350℃的基材溫度下便可沉積出最佳化鍍膜。

The great demand for petrochemical energy has led to the development of alternative power sources, such as solar cells, recent years and is expected to be clean energy source of the future. Development of solar cells from silicon-based devices to the new dye-sensitized type, referred to as dye-sensitized solar cells (DSSC), is a great step forward in this area, such as simpler fabrication techniques and reduced costs. The most common DSSC under current development is the titanium dioxide based type. Various production methods have been developed to fabricate TiO2 films for DSSC. The wet processes used are extensively investigated, but have disadvantages in terms of chemical by-products and the requirement for a post heat treatment, of over 400°C, in order to encourage anatase crystal growth. To overcome these short falls, vacuum deposition processes have been developed for the deposition of TiO2 layers.

In this study, an arc ion plating (AIP) system shall be used to prepare the TiO2 layer, as this process is environmentally friendly, clean, relatively uncomplicated and may reduce solar cell production costs. Deposition parameters including oxygen partial pressure, substrate bias, deposition pressure and deposition time are varied to examine their effects on the microstructure and photovoltaic efficiency of the TiO2 deposits in form of the device ITO glass/〔TiO2(N3 dye)〕/ I + LiI electrolyte/Pt/ITO glass.

Experimental results show that the increased oxygen partial pressure over 0.35 Pa favors the growth of stiochiometric TiO2 films, which are visually transparent and present anatase crystal structure. The substrate bias induces a denser film growth and hence higher transparency. When increasing deposition pressure, anatase phase become dominate and a loose film structure can be obtained due to thermalization effect. An excessive deposition pressure leads to the fine-grain growth of the deposit. In contrast to the thinner film deposited at shorter time, the thicker film presents less amount of rutile phase and high specific surface area. A dual-target AIP enhances the film growth rate.

In summary the microstructure mentioned above, short current as an indication of photovoltaic efficiency of the solar cell device composed of AIP-TiO2 can be increased by the increasing oxygen partial pressure due to the increased amount of high crystallinity stiochiometric TiO2 film. A negative effect to the short current can be found by applying substrate bias owing to the reduced specific surface area of the denser film. The increased deposition pressure although is beneficial to the growth of loose films which exhibit higher short current, an excessive deposition pressure would then cause the fine-grain growth of the deposit and eventually decrease short current. A longer deposition time facilitate a thicker film with lager specific surface area there by larger short current. Under a pure oxygen deposition condition without substrate bias, a TiO2 film deposited for 60 min posses a short current of 0.052 mA/cm2 in corresponding to a photovoltaic efficiency of 0.08%. The dual-target AIP system minimizes the deposition time into 30 min while results similarly.

Accordingly, the photovoltaic efficiency of AIP-TiO2 film is necessitated by the amount of anatase phase in the deposit. It is then determined by the specific surface area of the deposited film. It is recommended that an optimized TiO2 film can be obtained in a deposition condition with pure oxygen, under moderate deposition pressure whilst keeping no substrate bias for a satisfactory deposition time. Also noticeable is the substrate temperature can be below 350℃.

中文摘要 I
英文摘要 III
總目錄 VI
圖目錄 IX
表目錄 XIII
第一章 前言 1
第二章 文獻回顧 3
2-1 矽太陽能電池 3
2-1-1 單晶矽太陽電池 3
2-1-2 多結晶矽太陽能電池 6
2-1-3 非晶矽及其他種類太陽能電池 7
2-2 染料敏化太陽能電池 11
2-2-1 染料敏化太陽能電池的基本結構及其原理 11
2-2-2 影響染料敏化太陽能電池效率的因素 15
2-2-2-1 多孔奈米TiO2薄膜 15
2-2-2-2 敏化染料 16
2-2-2-3 載流子傳輸材料 17
2-3 染料敏化太陽能電池的二氧化鈦鍍層被覆技術 19
2-4 真空電弧法原理 22
2-4-1 電弧的產生 23
2-4-2 鍍膜參數之控制及其對微觀組織之預期影響 24
2-5 研究動機 27
第三章 研究方法與流程 28
3-1 基材準備 29
3-2 TiO2鍍膜製程最佳化 29
3-3 晶體結構與微觀組織分析 31
3-4 TiO2鍍膜光電轉換特性的量測 31
3-4-1 染料及電解質的製備 32
3-4-2 元件組裝 32
3-4-3 光電效率的量測 33
第四章 結果與討論 36
4-1 施鍍參數對鍍膜外觀的影響 36
4-1-1 氧氣分壓對TiO2鍍膜的外觀之影響 36
4-1-2 基材偏壓對TiO2鍍膜的外觀之影響 36
4-1-3 沉積壓力對TiO2鍍膜的外觀之影響 37
4-1-4 沉積時間對TiO2鍍膜的外觀之影響 38
4-2 施鍍參數對TiO2鍍膜的晶體結構之影響 39
4-2-1 氧氣分壓對TiO2鍍膜的晶體結構之影響 39
4-2-2 基材偏壓對TiO2鍍膜的晶體結構之影響 41
4-2-3 沉積壓力對TiO2鍍膜的晶體結構之影響 42
4-2-4 沉積時間對TiO2鍍膜的晶體結構之影響 43
4-2-5 雙電弧源不同沉積時間對TiO2鍍膜的晶體結構之影響 44
4-3 施鍍參數對TiO2鍍膜的顯微組織之影 45
4-3-1 氧氣分壓對TiO2鍍膜的顯微組織之影響 45
4-3-2 基材偏壓對TiO2鍍膜的顯微組織之影響 48
4-3-3 沉積壓力對TiO2鍍膜的顯微組織之影響 50
4-3-4 沉積時間對TiO2鍍膜的顯微組織之影響 52
4-3-5 雙電弧源不同沉積時間對TiO2鍍膜的顯微組織之影響 54
4-4 施鍍參數對TiO2鍍膜的光電流之影響 55
4-4-1 氧氣分壓對TiO2鍍膜的光電流之影響 55
4-4-2 基材偏壓對TiO2鍍膜的光電流之影響 56
4-4-3 沉積壓力對TiO2鍍膜的光電流之影響 58
4-4-4 沉積時間對TiO2鍍膜的光電流之影響 60
4-4-5 雙鈦靶不同沉積時間對TiO2鍍膜的光電流之影響 61
4-4-6 限制電弧離子鍍二氧化鈦光電轉換效率之探討 62
第五章 結論 64
參考文獻 66
誌謝 70

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