Contents List of Tables List of Figures Chapter 1 Introduction ………………………………………1 1.1 Background and Motivation ………………………………………………………1 1.2 Solar cell…………………………………………………………………..………3 1.2.1 Introduction to the solar cell…………………………………………………… 3 1.2.2 Basic theory of solar cell…………………………………………….………… 5 1.2.3 The Physical of the Solar Cell……………………………………….………… 6 1.2.4 The Current-Voltage Characteristic of an Infinite Solar Cell………….……… 9 1.2.5 Short Circuit Current ……………………………………………….…………10 1.2.6 Open Circuit Voltage……………………………………………….………… 11 1.2.7 Fill Factor…………………………………………………………..………… 12 1.2.8 Efficiency ………………………………………………………..……………13 1.2.9 Electrical Losses……………………………………………………………… 14 References…………………………………………………………...……………… 16 Chapter 2 Fabrication Processes……………...…………… 17 2.1 Formation of Porous Silicon layer……………………………………………… 17 2.2 P-N junction formation: Doping by diffusion using furnace ……………………18 2.3 Metallization………………………………………………………….………… 19 2.4 Deposition of anti-reflection layer (Si3N4) by HDP CVD……………………… 20 2.5 Grating solar cell with porous silicon…………………...……………………… 22 2.6 Process flow of device…………………………..……………………………… 24 References………………………………………...………………………………… 25 Chapter 3 Results and discussion………………………… 26 3.1 Characterization of porous structure solar cell………………………………… 26 3.1.1 Four point probe……………………………………………………………… 26 3.1.2 Scanning Electron Microscope (SEM) ………………….…………………… 28 3.1.3 Spreading Resistance Probe System (SRP) ……………..…………………… 30 3.1.4 Solar simulator…………………………………...…………………………… 31 3.2 Experimental results and discussions…………………………………………… 32 References………………………...………………………………………………… 61 Chapter 4 Conclusion and Future work………………… 63 List of Tables Table 1 Environment pollution due to various energy sources Table 2 High and low resistivity comparison table Table 3 Different etching condition on low resistivity wafer comparison table Table 4 All data with all conditions on the low resistivity wafer is shown Table 5 All data with high resistivity and low resistivity wafer is shown Table 6 The performance with HNO3 passivation List of Figures Figure 1-1 Share of various energy sources in the word Figure 1-2 Complexity of manufacturing Figure 1-3 Solar cell schematic drawing Figure 1-4 The electricity generation principle of solar cell Figure 1-5 The way to estimate the air mass Figure 1-6 The radiation spectrum for a black body at 5762 K, an AM0 spectrum,and an AM1.5 global spectrum. Figure 1-7 Voltage-current characteristic of an infinite solar cell Figure 1-8 Solar cell equivalent circuit Figure 1-9 Solar cell’s output power Figure 1-10 Loss mechanisms in a solar cell Figure 2-1 Schematic diagram of a Teflon bath for electrochemical etching Figure 2-2 Diffusion doping process Figure 2-3 Conceptual silicon oxidation system Figure 2-4 Schematic of the magnetron sputtering system with a shield Figure 2-5 Relationship of step coverage to pressure and surface mobility Figure 2-6 Gaps fill of high-density plasma CVD Figure 2-7 Standard RCA flow Figure 2-8 Experimental Step Figure 2-9 The process flow of the device Figure 3-1 Four-point probe measurement method. The outer two probes force a current through the sample; the inner two probes measure the voltage drop Figure 3-2 Surface analysis techniques used to identify and quantify contamination in IC manufacturing Figure 3-3 Energy distribution of electrons emitted from a solid under electron bombardment Figure 3-4 Band diagram representation of some of the processes used in surface analytical methods Figure 3-5 Schematic of a spreading resistance measurement where metal probes step down the surface of a beveled sample and measure the resistance between the probes at each step Figure 3-6 The total process and all kinds of analysis Figure 3-7 (a) ~ (c) Top view and cross-section view of SEM micrographs for p-type 9~11Ω. The organic electrolyte was 3M HF/DMSO. The applied current was 3 mA/cm2, and the total etching time was 40 minutes Figure 3-8 (a) ~ (c) Top view and cross-section view of SEM micrographs for p-type 9~11Ω. The organic electrolyte was 3M HF/DMSO. The applied current was 5 mA/cm2, and the total etching time was 40 minutes Figure 3-9 (a) ~ (c) Top view and cross-section view of SEM micrographs for p-type 1~3Ω. The organic electrolyte was 3M HF/DMSO. The applied current was 3 mA/cm2, and the total etching time was 40 minutes Figure 3-10 (a) ~ (c) Top view and cross-section view of SEM micrographs for p-type 1~3Ω. The organic electrolyte was 3M HF/DMSO. The applied current was 3 mA/cm2, and the total etching time was 60 minutes Figure 3-11 (a) ~ (c) Top view and cross-section view of SEM micrographs for p-type 1~3Ω. The organic electrolyte was 3M HF/DMSO. The applied current was 3 mA/cm2, and the total etching time was 90 minutes Figure 3-12 (a) ~ (c) Top view and cross-section view of SEM micrographs for p-type 1~3Ω. The organic electrolyte was 3M HF/DMSO. The applied current was 5 mA/cm2, and the total etching time was 40 minutes Figure 3-13 (a) ~ (c) Top view and cross-section view of SEM micrographs for p-type 1~3Ω. The organic electrolyte was 3M HF/DMSO. The applied current was 5 mA/cm2, and the total etching time was 60 minutes Figure 3-14 (a) ~ (c) Top view and cross-section view of SEM micrographs for p-type 1~3Ω. The organic electrolyte was 3M HF/DMSO. The applied current was 5 mA/cm2, and the total etching time was 90 minutes Figure 3-15 Experimental conditions and parameters Figure 3-16 CZ-furnaces Figure 3-17 The schematic drawing of porous silicon formation Figure 3-18 The band diagram of the interface between the semiconductor and the electrolyte Figure 3-19 Experimental conditions designed Figure 3-20 Efficiency comparison of all conditions on the low resistivity wafer Figure 3-21 Jsc comparison of all conditions on the low resistivity wafer Figure 3-22 Voc comparison of all conditions on the low resistivity wafer Figure 3-23 (a) ~ (b) Top view and cross-section view of SEM micrographs for p-type 1~3Ω. The organic electrolyte was 2M HF/DMSO. The applied current was 3 mA/cm2, and the total etching time was 40 minutes Figure 3-24 The results of spreading resistance probe system Figure 3-25 Comparison of high resistivity and low resistivity wafer. Figure 3-26 The Effect of Rs and Rp Figure 3-27 The finished products Figure 3-28 Performance comparison