本研究採用兩階段硒化法製備硒化銅銦鎵(CIGS)薄膜，其步驟為先沉積金屬前驅物，接著在過量硒氣的真空加熱環境下硒化金屬前驅物。探討兩階段硒化法之製程參數與CIGS薄膜特性和太陽能電池性能之間的相關性。結果顯示在相對高硒通量25Å/s條件下，硒化的CIGS薄膜呈現較佳的表面形貌。在給定的硒化條件下，CIGS太陽能電池效率達到12.5%。另外，討論不同的共蒸鍍法－單階段、雙層和三階段製程，與以共蒸鍍法製備CIGS薄膜之太陽能電池特性。CIGS薄膜表面形貌和薄膜內漸變式能帶寬結構，對於改善CIGS太陽能電池的開路電壓都具有決定性的影響。已經實現轉換效率超過17%的共蒸鍍CIGS太陽能電池，並找出控制CIGS太陽能電池性能的機制及關鍵因素。
　　此外，擬合高效率碲化鎘(CdTe)太陽能電池的元件效能曲線，開發出具有選定半導體特性的CdTe太陽能電池之基本模型和進階模型，分析提升高性能CdTe太陽能電池效率的主要因素。減少硫化鎘(CdS)薄膜厚度、低缺陷密度且高載子遷移率的CdS薄膜是提高短路電流密度的關鍵因素。隨著載子再復合的抑制，具低缺陷密度的CdTe薄膜或擴散層的CdTe太陽能電池，其開路電壓和填充因子因此提升。除此之外，高缺陷密度的擴散層阻礙載子收集，導致短路電流密度降低。模擬結果顯示，具有低缺陷密度和高載子濃度的CdTe薄膜，其太陽能電池效率達到20-21%。

The two-step process including the deposition of the metal precursors followed by heating the metal precursors in a vacuum environment of Se overpressure was employed for the preparation of Cu(In,Ga)Se2 (CIGS) films. The correlations among the two-step process parameters, film properties, and cell performance were studied. The results demonstrated that the CIGS films selenized at the relatively high Se flow rate of 25 Å/s exhibited the improved surface morphologies. With the given selenization conditions, the efficiency of 12.5% for the fabricated CIGS solar cells was achieved. The features of co-evaporation processes including the single-stage, bi-layer, and three-stage process were discussed. The characteristics of the co-evaporated CIGS solar cells were presented. Not only the surface morphologies but also the grading bandgap structures were crucial to the improvement of the open-circuit voltage of the CIGS solar cells. Efficiencies of over 17% for the co-evaporated CIGS solar cells have been achieved. Furthermore, the critical factors and the mechanisms governing the performance of the CIGS solar cells were addressed.
In addition, a baseline model and an advanced model of CdTe solar cells with the selected semiconductor properties fitting to the performance parameters of the champion CdTe solar cells were developed. The responsible factors for the efficiency improvement of the high-performance CdTe solar cell were analyzed. The thin CdS films, and the low defect densities and high carrier mobilities of the CdS films were the crucial factors for the enhancement of the short-circuit current density. With the suppression of carrier recombination, the open-circuit voltage and the fill factor of the CdTe solar cells with the low defect densities in either CdTe films or interdiffusion layer were enhanced. Furthermore, the carrier collection was impeded for the interdiffusion layer with a high defect density, leading to a decrease in the short-circuit current density. Moreover, the simulation results revealed that the efficiency of 20-21% was achieved for the CdTe solar cells with the low defect densities and the high carrier concentrations of the CdTe films.

Acknowledgements i
摘要 ii
Abstract iii
List of Figures vi
List of Tables viii
CHAPTER 1 Introduction 1
CHAPTER 2 Characteristics of CIGS Solar Cells Prepared by Various Deposition Methods 5
2.1 Introduction 5
2.2 Experimental Details 7
2.2.1 CIGS film preparation and device fabrication 7
2.2.2 Film and device characterization 8
2.3 Results and Discussion 9
2.3.1 Effects of Se flux rates on low and high Ga-content CIGS solar cells prepared by two-step process 9
2.3.2 Effects of Ga contents on co-evaporated CIGS solar cells 16
2.3.3 Characteristics of CIGS solar cells prepared by various deposition processes 18
2.4 Summary 26
CHAPTER 3 Investigation on Performance of CdTe Solar Cells Using Simulation Approaches 29
3.1 Introduction 29
3.2 Device Modeling 30
3.3 Results and Discussion 32
3.3.1 Baseline model and advanced model 32
3.3.2 Analysis of critical factors impacting the performance of CdTe solar cells 35
3.3.3 Efficiency beyond 20% 40
3.4 Summary 42
CHAPTER 4 Conclusions 45
References 47

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