Fabrication and characterization of grade doped InGaP/InGaAs/Ge triple-junction solar cells grown by MOVPE
- 주제(키워드) Solar cells , graded doping concentration , III-V compound semiconductors , photovoltaics , multi-junction , tandem , power conversion efficiency , metalorganic vapor phase epitaxy , epitaxial growth
- 발행기관 아주대학교
- 지도교수 이재진
- 발행년도 2016
- 학위수여년월 2016. 8
- 학위명 박사
- 학과 및 전공 일반대학원 전자공학과
- 실제URI http://www.dcollection.net/handler/ajou/000000023218
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
III-V Compound semiconductor based multi-junction solar cells have been studied for the space photovoltaic and high efficiency concentrator solar cell applications. Recently, compound semiconductor based multi-junction solar cells have been reported on 46 % efficiency under high concentrated illuminations. The enhancement of photovoltaic conversion efficiency by optimizing the epitaxial structure of sub-cells is essential to further understand the multi-junction structures and realize higher efficiency. In this dissertation, I analyzed the graded doping effect of emitter and base layers on the performances of the InGaP/InGaAs/Ge triple-junction solar cells grown by metalorganic vapor phase epitaxy. I investigate the computer simulation and experimental results of photovoltaic conversion efficiency of the GaAs and InGaP single-junction and InGaP/InGaAs triple-junction solar cells as a function of the graded doping in the emitter and base using TCAD tool (APSYS 2010). The various solar cells are fabricated using a standard photolithography, metal deposition, rapid thermal annealing, wet-chemical etching processes, and chip isolations. Photovoltaic device parameters and conversion efficiency of the cells are measured under AM1.5 global light illuminations. First, the GaAs and InGaP single-junction and InGaP/InGaAs/Ge triple-junction solar cells have been simulated by varying the uniformly and graded doped emitter and base structures. In the GaAs single-junction solar cells with graded doped emitter and base layer, the sample with graded doped emitter and base layer has the higher photovoltaic conversion efficiency than that of other samples. In the InGaP single-junction solar cells with graded doped emitter and base layer, the sample with graded doped emitter and base layer has the higher photovoltaic conversion efficiency than that of other samples. In the InGaP/InGaAs/Ge triple-junction solar cells with graded doped top and middle cells emitter and base layers, the sample with graded doped emitter and base layer has the higher photovoltaic conversion efficiency than that of other samples. The graded doping concentration and Fermi level profiles of GaAs and InGaP single-junction and InGaP/GaAs/Ge triple-junction solar cells are studied. Second, the GaAs single-junction solar cells have been epitaxially grown on GaAs substrates using MOVPE by varying the graded doped emitter and base layer structures. I prepared four different GaAs single-junction solar cells having the uniformly doped emitter and base layer, the graded doped emitter and uniformly doped base layer, the uniformly doped emitter and graded doped base layer, and the graded doped emitter and base layer. Photovoltaic device parameters and external quantum efficiency of the GaAs single-junction cells are characterized under the one-sun and high concentration illuminations. For sample with graded doped base layer, higher photovoltaic conversion efficiency, short circuit current density and external quantum efficiency are measured as compared to other samples. The open circuit voltage of sample with graded doped emitter and base layer is higher than that of other samples. Third, the InGaP single-junction solar cells have been epitaxially grown on GaAs substrates using MOVPE by varying the graded doped emitter and base layer structures. I prepared four different InGaP single-junction solar cells having the uniformly doped emitter and base layer, the graded doped emitter and uniformly doped base layer, the uniformly doped emitter and graded doped base layer, and the graded doped emitter and base layer. Photovoltaic device parameters and external quantum efficiency of the InGaP single-junction cells are characterized under the one-sun and high concentration illuminations. For sample with graded doped emitter layer, higher photovoltaic conversion efficiency, short circuit current density and external quantum efficiency are measured as compared to other samples. The open circuit voltage of sample with graded doped emitter and base layer is higher than that of other samples. Finally, the InGaP/InGaAs/Ge triple-junction solar cells have been epitaxially grown on Ge substrates using MOVPE by varying the graded doped emitter and base layer structures. I prepared three different InGaP/InGaAs/Ge triple-junction solar cells having the uniformly doped top and middle cell emitter and base layer, the graded doped top cell emitter and middle cell base layer, and the graded doped top and middle cell emitter and base layer. Photovoltaic device parameters and external quantum efficiency of the InGaP/InGaAs/Ge triple-junction cells are characterized under the one-sun and high concentration illuminations. For sample with the graded doped top cell emitter and middle cell base layer, higher photovoltaic conversion efficiency, short circuit current density and external quantum efficiency are measured as compared to other samples. The open circuit voltage of sample with graded doped middle and top cell emitter and base layer is higher than that of other samples. The photovoltaic conversion efficiency of InGaP/InGaAs/Ge triple-junction solar cell is 40.46 % at 159.74 suns concentration illuminations.
more목차
Chapter 1. Introduction 1
1.1. Solar cells 1
1.2. Limit of single-junction solar cells 9
1.3. Multi-junction solar cells 11
1.4. Concentrator Photovoltaic (CPV) 23
1.5. Doping concentration of solar cells 33
1.6. Research objective and outline 43
Chapter 2. Experimental methods 45
2.1. Epitaxial growth and analysis of solar cell structure 45
2.2. Fabrication process for solar cells 50
2.3. Characterization of solar cells 53
Chapter 3. Computer simulation of III-V compound semiconductor based solar cells with various doping structures 55
3.1. Introduction 55
3.2. Computer simulation 57
3.2.1. Computer simulation of GaAs single-junction solar cells with graded doping concentration 57
3.2.2. Computer simulation of InGaP single-junction solar cells with graded doping concentration 61
3.2.3. Computer simulation of InGaP/InGaAs/Ge triple-junction solar cells with graded doping concentration 63
3.3. Simulation results and discussion 65
3.3.1. GaAs single-junction solar cells with uniformly doped base layer 65
3.3.2. GaAs single-junction solar cells with graded doped base layer 74
3.3.3. GaAs single-junction solar cells with graded doped emitter and base layer 83
3.3.4. InGaP single-junction solar cells with graded doping concentration 94
3.3.5. InGaP/InGaAs/Ge triple-junction solar cells with graded doping concentration 105
3.4. Conclusion 117
Chapter 4. Efficiency enhancement of GaAs single-junction solar cells with graded doping structures 118
4.1. Introduction 118
4.2. Experimental 121
4.2.1. Epitaxial growth of GaAs single-junction solar cell with graded doping 121
4.2.2. Device fabrication of GaAs single-junction solar cell with graded doping 123
4.3. Results and discussion 125
4.3.1. Photovoltaic device characteristics 125
4.3.2. Efficiency and short circuit current density 128
4.3.3. External quantum efficiency analysis 130
4.3.4. Open circuit voltage analysis 133
4.3.5. Photovoltaic device characteristics in concentration 135
4.4. Conclusion 140
Chapter 5. Efficiency enhancement of InGaP single-junction solar cells with graded doping structures 141
5.1. Introduction 141
5.2. Experimental 143
5.2.1. Epitaxial growth of InGaP single-junction solar cell with graded doping 143
5.2.2. Device fabrication of InGaP single-junction solar cell with graded doping 145
5.3. Results and discussion 147
5.3.1. Photovoltaic device characteristics 147
5.3.2. Efficiency and short circuit current density 150
5.3.3. External quantum efficiency analysis 152
5.3.4. Open circuit voltage analysis 155
5.3.5. Photovoltaic device characteristics in concentration 157
5.4. Conclusion 162
Chapter 6. Efficiency enhancement of InGaP/InGaAs/Ge triple-junction solar cells with graded doping structures 163
6.1. Introduction 163
6.2. Experimental 165
6.2.1. Epitaxial growth of InGaP/InGaAs/Ge triple-junction solar cell with graded doping 165
6.2.2. Device fabrication of InGaP/InGaAs/Ge triple-junction solar cell with graded doping 168
6.3. Results and discussion 170
6.3.1. Photovoltaic device characteristics 170
6.3.2. Efficiency, short circuit current density, and open circuit voltage 174
6.3.3. External quantum efficiency analysis 178
6.3.4. Open circuit voltage analysis 180
6.3.5. Photovoltaic device characteristics in concentration 182
6.4. Conclusion 189
Chapter 7. Conclusion and Future work 190
7.1. Conclusion 190
7.2. Future work 192
References 193
Research achievements 207
