單晶矽太陽電池所使用的矽晶片傾向於越來越薄(<200μm)，但結晶矽具間接能隙造成光吸收係數偏低，因此需要借助鈍化層(passivation)、光捕捉(light trapping)等技術以達成高效率太陽電池之元件設計，然而隨著矽晶片厚度減薄至幾十微米的程度，既有的光捕捉技術將難以施展。本實驗室多年研究Cu-III-VI族半導體材料性質並有效改善薄膜磊晶技術，期藉由具直接能隙之CuGaSe2和CuInSe2薄膜搭配超薄矽晶片(10~50μm)，前者與矽形成異質接面而後者以其優越的光吸收特性解決矽晶片薄化的問題，此一新穎的太陽電池元件結構為p-CuGaSe2/n-Si/n-CuInSe2。由於異質材料界面缺陷與N型CuInSe2高電阻率等問題，目前以矽晶同質接面搭配CuInSe2(即n-Si/p-Si/p-CuInSe2)進行初步研究，一則探討CuInSe2/Si磊晶問題，再則進行元件模擬以了解材料性質的影響程度。
在這項研究中，我們利用共蒸鍍系統製備CuInSe2薄膜，在(100)單晶矽晶片上嘗試磊晶，初步結果由XRD判斷形成富銦之Cu2In4Se7相，由歐傑能譜縱深分析判斷該薄膜中各元素比例組成偏離定比值頗大，需要做製程上的調整。另一方面以鋅摻雜未能成功形成低電阻之N型CuInSe2。在模擬軟體PC1D計算方面，10微米矽晶同質接面搭配最佳化摻雜濃度之CIS可由19.5%提升到28%之高效率。

As the Si wafer tends to decrease in thickness for current developments of crystalline Si solar cells, light trapping becomes a crucial technology to enhance optical absorption in crystalline Si to achieve high energy conversion efficiency. We propose the use of CuInSe2 (CIS), an effective optical absorbed layer due to its direct bandgap of 1.03 eV, to grow epitaxially on the back of single-crystalline Si wafer and eliminate the light trapping design needed for conversional Si solar cells. This technique is even more powerful for its application on ultra-thin Si wafers (10~50 μm). In this work, we grew CIS epitaxial films on (100)Si wafers by three-source evaporation. XRD analysis indicated that the film grown epitaxially on Si, but the crystalline phase was identified to be Cu2In4Se7, a defect-ordered chalcopyrite compound. Auger depth profiling showed that the Cu:In ratios are 1:2 in the film and 1:3 at the surface for the film grown at 500oC and annealed in Se overpressure at 400oC for 30 minutes. Also, the Se content was significant lower than the expected value in the film but increased slightly near to the surface. The discrepancy of the film composition far from the stoichiometry of a chalcopyrite phase, i.e. Cu:In:Se=1:1:2, was attributed to the different evaporation rate of Cu2Se and In2Se3, which were formed prior to react to be a CIS compound. In addition, the Auger data revealed an amount of 5~10 at% Si in the film, which might be caused by the interdiffusion between the film and the substrate. Therefore, a low-temperature growth process, such as photo-assisted molecular beam epitaxy, should be employed for the CIS growth. On the other hand, extrinsic doping of Zn in CIS was investigated but not got a successful result. This suggests that an alternate candidate of group II element with less electronegativity, such as Cd, may be used to replace Zn as an effective n-type dopant. Finally, a PC1D simulation tool was applied to predict and optimize the device properties of a Si homojunction capped with a CIS bottom layer, i.e. n-Si/p-Si/p-CIS. We found that an increase in cell efficiency up to 28% for an ultra-thin (10 m) Si solar cell could be realized through the addition of a CIS layer with an optimized doping concentration.

摘要 ii
Abstract iii
圖目錄 vi
表目錄 viii
一、 導論 1
1-1 前言 1
1-2 矽晶太陽電池 5
1-3 CuInSe2材料基本性質 9
1-4 SiCIS元件設計 12
1-5 研究動機與目的 16
二、 實驗及分析方法 18
2-1 實驗規劃及實驗流程 18
2-1-1 元件模擬方法 19
2-1-2 元件各層膜製備與製程儀器簡介 23
2-2 分析儀器 28
2-2-1 X光繞射儀 28
2-2-2 拉曼光譜儀 28
2-2-3 四點探針 29
2-2-4 穿透光譜儀 30
2-2-5 場發式掃描電子顯微鏡 31
2-2-6 電流-電壓特性曲線量測(I-V measurement) 31
2-2-7 歐傑電子能譜儀(auger electron spectroscopy ,AES) 31
三、 實驗結果與討論 33
3-1 製備CuInSe2定比組成 33
3-2 CIS共蒸鍍於矽晶基板 40
3-3 元件模擬結果 45
3-4 N型矽之上電極金屬選擇 49
3-5 CIS摻雜Zn 51
四、 結論 53
五、 參考文獻 54

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