Surface and bulk passivation of multicrystalline silicon solar cells by ...

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11 examples of third generation technologies: multijunction photovoltaic cells, quantumwell or other nano-structure sοlαr cells, dye-sensitized solαr cells, organic/polymer sοlαr cells, concentration systems and excess thermal generation approaches to enhance voltages or carrier collection [24]. 1.3.2 Silicon Solar Cells The work presented in this dissertation focuses on problems relating to methods to improve efficiencies of crystalline silicon solar cells. Silicon is not only the material used in the earliest successful PV devices, but continues to remain as the most widely used PV material. Over 95% of all the solar cells produced worldwide are composed of Si. As the second most abundant element in the earth's crust, silicon has the advantage of being available in sufficient quantities. A roadmap of solar cell production and capacity is shown in Figure 1.5 [28]. Figure 1.5 Solar cell production and capacity [28]. The statistics and predictions indicate that crystalline silicon solar cells were, are and will be the dominant influence in the PV industry.
12 Basically, materials for manufacturing silicon solar cells can be distinguished according to the type of crystal into three categories: monocrystalline, polycrystalline and amorphous. In order to produce a monocrystalline silicon cell, absolutely pure semiconductor material is necessary. Monocrystalline rods are extracted from melted silicon and then sawed into thin plates. This production process guarantees a relatively high level of efficiency. The production of polycrystalline cells is more cost-efficient. In this process, liquid silicon is poured into blocks that are subsequently sawed into plates. During solidification of the material, crystal structures of varying sizes are formed, at whose borders defects emerge. As a result of this crystal defect, the solar cell is less efficient. If a silicon film is deposited on glass or another substrate material, this leads to the so-called amorphous or thin layer cell. The layer thickness amounts to less than 1 μm; so the production costs are lower due to the low material costs. However, the efficiency of amorphous cells is much lower than that of the other two cell types. Because of this, they are primarily used in equipment that require low power (watches, pocket calculators) or as facade elements. Silicon solar cell technology has greatly advanced in the past three decades. Crystalline silicon is the dominant material in today's photovoltaic industry, and is expected to remain so in the coming decades (~ 80% of solar cells produced at present are crystalline silicon solar cells and the remaining 20% are mostly nonsilicon solar cells) [28]. 1.4 Structure of A Crystalline Si Solar Cell Crystalline silicon is the primary example of a homojunction solar cell. A single crystal silicon is altered so that one side is p-type, dominated by positive holes, and the other side is n-type, dominated by negative electrons. The p/n junction is located
Page 1 and 2: Copyright Warning & Restrictions Th
Page 3 and 4: ABSTRACT SURFACE AND BULK PASSIVATI
Page 5 and 6: SURFACE AND BULK PASSIVATION OF MUL
Page 7 and 8: APPROVAL PAGE SURFACE AND BULK PASS
Page 9 and 10: Chuan Li, B.L. Sopori, P. Rupnowski
Page 11 and 12: ACKNOWLEDGEMENT The work presented
Page 13 and 14: TABLE OF CONTENTS (Continued) Chapt
Page 15 and 16: LIST OF TABLES Table Page 2.1 Posit
Page 17 and 18: LIST OF FIGURES (Continued) Figure
Page 19 and 20: LIST OF FIGURES (Continued) Figure
Page 21 and 22: 2 percent; however, soon, more adva
Page 23 and 24: 4 Figure 1.1 World solar module pro
Page 25 and 26: 6 bond is called a hole. It too can
Page 27 and 28: 8 Figure 1.4 The I-V characteristic
Page 29: 10 First generation cells consist o
Page 33 and 34: 14 Defects are generally categorize
Page 35 and 36: 16 copper, or nickel in concentrati
Page 37 and 38: 18 the SiNx:H layer during the ther
Page 39 and 40: CHAPTER 2 SILICON NITRIDE LAYER FOR
Page 41 and 42: 22 reflectance of polished Si can b
Page 43 and 44: 24 information is application-orien
Page 45 and 46: 26 film fed growth (EFG) ribbon sil
Page 47 and 48: 28 Figure 2.5 Deposition of SiΝ :
Page 49 and 50: 30 Figure 2.6 shows the dependence
Page 51 and 52: 32 atoms, the interface states are
Page 53 and 54: 34 2.5 Bulk Passivation of Si by Si
Page 55 and 56: 36 It was found that the bulk lifet
Page 57 and 58: CHAPTER 3 MODELING OF SURFACE RECOM
Page 59 and 60: 40 Figure 3.2 Schematic diagram of
Page 61 and 62: 42 σ and σp are the capture cross
Page 63 and 64: 44 Qsi — charge density induced i
Page 66 and 67: 47 Figure 3.5 The calculated depend
Page 68 and 69: 49 * 10 Λ m; m is in a range from
Page 70 and 71: 51 Na, sigma_n, sigma_p: enter x.xx
Page 72 and 73: 53 Figure 3.7 Measured Seff(Δn) de
Page 74 and 75: 55 curves converge to a single valu
Page 76 and 77: 57 seen that, initially Ss decrease
Page 78 and 79: 59 carrier recombination within the
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61 recombination in the SCR influen
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63 Figure 3.13 shows that: 1) after
Page 84 and 85:
CHAPTER 4 MINORITY-CARRIER LIFETIME
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67 Figure 4.1 Α photograph of QSSP
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69 work. The most convenient is 1 m
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7Ι dependence of the minority carr
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73 It was tempting to assume that l
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75 resistivities and lifetime) do n
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77 5.2 Objective An electronic mode
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79 Figure 5.2 is a photograph of a
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81 impurity-gettering methods which
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83 distribution of local currents a
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85 modeling. Wafers were selected f
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87 Figure 5.5 A comparison of (a) d
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89 alloying results in metallizatio
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91 (i) Defect clusters are the prim
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93 SiNX induced charge density on t
Page 114 and 115:
APPENDIX I PROGRAMS TO CALCULATE SR
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97 phin = -ΕΙ - 1 / beta * log(nd
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99 ίter3 = 0 for xi=1 to nmax/2-1
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101 input "output file name {XXXXXX
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103 F (i) = (exp (beta * (phip - ph
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APPENDIX III COMPUTATIONAL METHOD F
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107 where, dscr is the width of the
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REFERENCES 1. E. Becquerel , C. R.
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44. L.L. Alt, S.W. Ing. Jr. and K.W
Page 132 and 133:
90. B.L. Sopori, Y. Zhang, and N.M.
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Surface and bulk passivation of multicrystalline silicon solar cells by ...

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