臺灣博碩士論文加值系統

In this thesis we developed sputtering process of CIGS absorber layers using a single quaternary-CIGS target. CIGS films were prepared without post-selenization by one-step RF sputtering at different substrate temperature. Additionally, a series of analysis on CIGS films was performed.
Two kinds of quaternary-CIGS targets with different composition were used in this thesis. One is copper-rich and the other is copper-poor. (The composition ratio of the copper-rich is Cu: 22.7 %, In: 18.2 %, Ga: 8.1 %, Se: 51.0 % and the composition ratio of the copper-poor is Cu: 18.0 %, In: 18.2 %, Ga: 8.1 %, Se: 55.7 %.) To investigate properties of CIGS films, it was observed that second phases of copper selenide and indium selenide occurred during fabrication of CIGS films. The copper-selenide phase is conductive and a leakage-current path in CIGS films. Hence we altered the 22%-Cu target into the 18%-Cu target in order to suppress the formation of Cu-Se phases.
Finally, the efficiency of 4.04% was achieved and the effective area up to 0.2 cm2. The CIGS solar cell fabricated by sputtering process without post-selenization is feasible.

Contents
Chapter 1 Introduction 1
Chapter 2 Background 3
2-1 Introduction of photovoltaic devices 3
2-1-1 What is photovoltaics? 3
2-1-2 Solar radiation spectrum 5
2-1-3 Basic principle of solar cells 7
2-1-3-1 I-V characteristic of solar cells 10
2-1-3-2 C-V characteristic of solar cells 13
2-2 Basic characterization of CIGS absorbed layers 16
2-2-1 Introduction of CIGS thin-film solar cells 16
2-2-2 Optical properties of CIGS absorber layers 18
2-2-2-1 Absorption coefficient of CIGS absorber layers 18
2-2-2-2 Tunable direct band gap of CIGS absorber layers 19
2-2-3 Electrical properties of CIGS absorber layers 24
2-2-3-1 Effects of intrinsic defects in CIGS absorber layers 24
2-2-3-2 Interfaces at the two sides of CIGS absorber layers 28
2-2-3-3 Effects of Sodium in CIGS absorber layers 31
2-2-4 Structural properties of CIGS absorber layers 34
2-2-4-1 CIGS orientation issue 36
2-2-4-2 Second phase issue in CIGS absorber layers 38
Chapter 3 Experiment Procedure 40
3-1 Experiment Flow Chart 40
3-2 RF Magnetron Sputtering System 41
3-3 X-Ray Diffraction (XRD) 42
3-4 Transmission Electron Microscopy (TEM) 43
3-5 Field-emission Scanning Electron Microscopy (FE-SEM) equipped with an energy dispersive X-ray spectrometer (EDX) 45
3-6 Solar Simulator and Keithley 4200-SCS 46
3-7 Raman Spectroscopy 47
3-8 Inductively Coupled Plasma-Mass Spectrometer (ICP-MS) 48
3-9 UV-Visible Near IR Absorption Spectroscopy 49
Chapter 4 Results and Discussions 50
4-1 Introduction 50
4-2 Experiment Procedure 51
4-3 Basic analysis of CIGS films sputtered with 22%-Cu target 52
4-3-1 Energy band gap of CIGS films 53
4-3-2 X-ray diffraction of CIGS films 54
4-3-3 Composition ratio of CIGS films 56
4-3-4 Efficiency of CIGS thin film solar cells 57
4-3-5 Brief results and discussions 58
4-4 Analysis of CIGS films deposited with 22%-Cu target 59
4-4-1 XRD of CIGS films 59
4-4-2 SEM of CIGS films 62
4-4-3 TEM-EDX of CIGS films 65
4-4-4 Raman spectroscopy of CIGS films 68
4-4-5 Composition ratio of CIGS films 70
4-4-6 SIMS of CIGS films 72
4-4-7 KCN issue on the second phase of Cu2Se in CIGS films 73
4-4-8 Brief results and discussions 76
4-5 Analysis of CIGS films deposited with 18%-Cu target 78
4-5-1 XRD of CIGS films 78
4-5-2 SEM of CIGS films 80
4-5-3 Composition ratio of CIGS films 83
4-5-4 Energy band gap of CIGS films 85
4-5-5 Raman spectroscopy of CIGS films 86
4-5-6 Resistivity of CIGS films 90
4-5-7 Efficiency of CIGS thin film solar cells 92
4-5-8 Brief results and discussions 93
Chapter 5 Conclusion 95
References 96

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