此研究專注於運用矽與有機材料的異質接面，以低成本的方式成倍提升太陽能電池效率。透過結合電子選擇性背電極與使用等向-非等向交互蝕刻製程，我們實現了以n型結晶矽材與p型電洞導電聚合物(PEDOT:PSS)為基礎的實驗。在此實驗中，藉由結合額外的電子選擇性氟化锂(LiF)背電極，我們達成高達14.3%的能量轉換效率(power conversion efficiency, PCE)，與高濃度摻雜的非晶矽背電極相比，此氟化锂背電極額外提供了調變功函數的功效，作為一個電子傳輸層，它同時改善了電流密度與功函數，分別達到3.5 mA/cm2與3.8 eV。此外，透過反向金屬輔助化學蝕刻(reverse-etched metal-assisted chemical etching)製程，我們可以良好控制奈米結構的型態，形成與PEDOT:PSS相容的接面，將反射率維持在5%以下。總結上述，此研究為提升電流密度、接面品質與Si/PEDOT:PSS異質接面太陽能電池效率提供了一個全新的方向與見解。

This research is based on heterojunctions of silicon and organic materials, which displayed a potential for enhancing the solar cell efficiency manifolds in a cost-effective way. Investigations based on texturized n-type crystalline silicon with the p-type hole conductive polymer, i.e., PEDOT:PSS for silicon heterojunction solar cell, were realized through the incorporation of electron-selective back contact along with the isotropic-anisotropic reverse etching process. In this work, by incorporating an additional electron-selective lithium fluoride (LiF) back contact, the power conversion efficiency (PCE) increased to 14.3%. Comparable to the heavily doped amorphous-Si back passivation layer, this LiF layer provided the functionality of modulating the work function. As an electron transporting layer, it improves the current density to 3.5 mA/cm2 and the work function from 4.3 eV (Si/Al) to 3.8 eV (LiF/Al). Additionally, based on the reverse-etched metal-assisted chemical etching (RE-MaCE) process, the nanostructured morphology can be controlled to form a coherent junction with PEDOT:PSS. The reflectance was maintained to be less than 5%. To summarize, this work provides a new insight to improve the current density, junction quality, and performance of nanostructured Si/PEDOT:PSS heterojunction solar cells.

List of Figures vii
Glossary xi
CHAPTER 1 Introduction 14
1.1 Timeline 14
1.2 Solar Cell 17
1.2.1 Heterojunction Solar cell 19
1.3 Solar Cell Physics 22
1.3.1 Electrical Characterstics 22
1.3.1.1 Photogeneration of Carriers 22
1.3.1.2 Carrier Concentration 22
1.3.1.3 P-N junction 25
1.3.1.4 Related Terminoligies 27
1.3.2 Optical Characterstics 30
1.3.2.1 Light Trapping 30
1.4 Silicon Nanowires 33
1.4.1 Geometry of Silicon Nanowires 34
1.4.2 Physics of Radial Junction 35
1.4.3 Introduction of PEDOT 36
1.4.4 Review on SiNWs/PEDOT hybrid solar cell 40

CHAPTER 2 Fabrication of Silicon Nanowires 42
2.1 Mechanism of Metal Assisted Chemical Etching(MaCE) 42
2.2 Experimental Procedure 44
2.3 Morphology Study 46

CHAPTER 3 Material and Sample Characterization 51
3.1 Materials 52
3.2 Experimental 53
3.3 Device Architecture 54
3.4 Sample Characterization 55
3.4.1 Solar Simulation. 55
3.4.2 Scanning Electron Microscopy(SEM) 56
3.4.3 Atomic Force Microscopy(AFM) 56
3.4.4 UV-Vis Spectroscopy. 57
3.4.5 Contact Angle. 57
3.4.1 Photoelectron Spectroscopy. 58

CHAPTER 4 Results 59
4.1 Optimization parameters for textured Si 59
4.1 Function of Triton X-100 63
4.1 Electron Selective Contact Analysis 66

CHAPTER 5 Discussion 71
5.1 Losses 71
5.2 Contact 72

CHAPTER 6 Conclusion 75

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