臺灣博碩士論文加值系統

為了達到高效率、低成本的太陽能電池，全矽材料串接太陽能電池是很有潛力的。將不同能隙之矽奈米結晶量子點薄膜堆疊可減少高能量光子的損耗，以提高效率。一般，大部分的實驗室會將矽奈米結晶埋在SiO2、Si3N4或SiC的材料中，但這些材料的導電性不好，造成此結構所形成之太陽能電池的效率比理論上低。為了改善此問題，我們提出將導電性較好的摻鋁氧化鋅材料應用在矽奈米結晶量子點薄膜中。
我們分析不同鋁含量對矽奈米結晶量子點薄膜的影響。當鋁的含量增加，奈米結晶矽量子點的大小和矽結晶率會減少。鋁的摻雜會抑制矽的成長。而矽奈米結晶量子點薄膜的導電性會隨著鋁含量增加而增加。但太粗糙的表面型態會使導電性減少。在多層薄膜與矽基板界面處的氧化矽和退火完的薄膜彎曲等兩個問題尚須解決。
為了解決界面氧化矽的問題，我們發展p型氧化鋅薄膜來取代矽基板。樣品在適當的氮流量、工作壓力和退火條件製程下會具有p型特性。我們演示了氧化鋅p-n同質接面並具有二極體的整流現象。
矽奈米結晶量子點埋入摻鋁氧化鋅薄膜的裝置成功演示出。若未來可解決界面氧化層和退火完薄膜彎曲的問題，此裝置將有潛力應用於太陽能電池中。

In order to achieve high efficiency and low cost solar cells, all silicon-based tandem solar cells including the nano-crystalline silicon (nc-Si) quantum dots (QDs) are proposed. The nc-Si QD thin films stacking with different bandgaps can reduce the high energy photon loss, so the efficiency can be improved. In general, most groups will embed nc-Si QDs in the Si-based materials, such as SiO2, Si3N4, and SiC. Because of poor conductivity of these materials, the efficiency is still substantially lower than the theoretical value. In this study, we propose to embed nc-Si QDs in the Al-doped ZnO (AZO) matrix.
We study the effect of the Al concentration on the nc-Si QD thin films. As the Al concentration increases, the nc-Si QD size and Si crystallinity decrease. The addition of Al suppresses the growth of Si. The conductivity of the nc-Si QD thin films increases with the increase of the Al concentration. However, the rougher surface morphology possibly causes the conductivity to decrease. The silicon oxide layer between the multilayer thin film and the Si substrate and the bending films after annealing are two problems need to be solved.
In order to solve the silicon oxide layer at the interface, we develop the p-type N-doped ZnO thin films to replace the Si substrates. The samples with suitable N2 flow, working pressure, and annealing conditions show the p-type properties. We demonstrate the ZnO p-n homojunction and examine the device has a diodelike rectification characteristic.
The device of the nc-Si QDs embedded in the AZO matrix has been demonstrated. If we solve the silicon oxide layer at the interface and bending films after annealing in the future, the device is a promising structure for solar cell applications.

Chapter 1 Introduction
1.1 Background 1
1.2 Solar Cells 2
1.3 Solar Cells with Multiple bandgaps 3
1.3.1 Power Loss Mechanisms 3
1.3.2 Effective Bandgap Engineering 5
1.3.3 All Si-based Tandem Solar Cells 6
1.4 Paper Review 7
1.4.1 Al-doped ZnO Thin Films 7
1.4.2 Nano-crystalline Silicon Quantum Dot Solar Cells 7
1.4.3 p-type ZnO Thin Films 10
1.5 Motivation 11
Chapter 2 Fabrication Process and Analyzing Method
2.1 Fabrication Process 13
2.1.1 Substrate Clean 13
2.1.2 Thin Film Deposition 14
2.1.3 Sample Annealing Process 17
2.1.4 Electrode Deposition 18
2.2 Analyzing Method 18
2.2.1 Four-Point Probe 18
2.2.2 Current-Voltage Measurements 19
2.2.3 High Resolution X-Ray Diffractometer 19
2.2.4 High Resolution Confocal Raman Microscope 20
2.2.5 UV/VIS/NIR Spectrophotometer 21
Chapter 3 Characterization of the Nano-crystalline Si Quantum Dots Embedded in the Al-doped ZnO Thin Films
3.1 Characterization of the Al-doped ZnO Thin Films 23
3.2 Influence of Different Annealing Temperatures 25
3.3 Influence of Different Al Concentrations 27
3.4 Comparison of the Nano-crystalline Si Quantum Dots Embedded in the ZnO and Al-doped ZnO Thin Films 32
3.5 Problems of the Nano-crystalline Si Quantum Dots Embedded in the Al-doped ZnO Thin Films 35
Chapter 4 Characterization of the p-type ZnO Thin Films
4.1 Analysis of High Resolution Confocal Raman Microscope 39
4.2 Analysis of Current-Voltage Characteristics 41
4.3 Analysis of ZnO p-n Homojunctions 45
Chapter 5 Conclusion and Future Work
5.1 Conclusion 47
5.2 Future Work 48
Reference
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