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

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75 resistivities and lifetime) do not have same dependence of lifetime on the light exposure. However, it was consistently seen that lower lifetime wafers had less dependence on the light exposure (i.e. they stabilize faster). Further investigations are being done to understand the observed time dependence of the measured lifetime. Based on these results, a simple model for wafer preparation was proposed as shown in Figure 4.7. Figure 4.7 Α wafer with a shallow (200-300 A) contaminated surface layer (a), after cleaning (b) and surface passivation (c) [108].
CHAPTER 5 EFFICIENCY LIMITATIONS CAUSED BY DEFECT CLUSTERS 5.1 Background One of the approaches to reduce the cost of commercial Si solar cells is to use lower-cost, multicrystalline Si (me-Si) substrates instead of single-crystal wafers. This approach has gained increasing acceptance by the photovoltaic (PV) industry and, as a result, the use of mc-Si has grown steadily to about 60% of the total Si-based solar cell production. The success of mc-Si as a cost-effective solar cell material is due primarily to the fact that advanced processing techniques, such as impurity gettering and hydrogen passivation, which are used in current solar cell fabrication, have worked very well in enhancing cell performance. These processing methods have led to efficiency of mc-Si solar cells exceeding 14%, which is slightly below that of commercial crystalline Si (c-Si) solar cells. However, further improvement in cell efficiency has proven difficult to achieve. Recent research has found that, in spite of using extensive gettering and passivation, mc-Si solar cells exhibit regions of low photoresponse and concomitant poor material quality. These local, low-response regions have a crystal structure that is not amenable to gettering, and constitute a new performance-limiting mechanism. By analysis of the structure of these regions, a new type of defect configuration was found, now called a defect cluster [109]. 76
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Copyright Warning & Restrictions Th
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ABSTRACT SURFACE AND BULK PASSIVATI
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SURFACE AND BULK PASSIVATION OF MUL
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APPROVAL PAGE SURFACE AND BULK PASS
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Chuan Li, B.L. Sopori, P. Rupnowski
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ACKNOWLEDGEMENT The work presented
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TABLE OF CONTENTS (Continued) Chapt
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LIST OF TABLES Table Page 2.1 Posit
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LIST OF FIGURES (Continued) Figure
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LIST OF FIGURES (Continued) Figure
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2 percent; however, soon, more adva
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4 Figure 1.1 World solar module pro
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6 bond is called a hole. It too can
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8 Figure 1.4 The I-V characteristic
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10 First generation cells consist o
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12 Basically, materials for manufac
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14 Defects are generally categorize
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16 copper, or nickel in concentrati
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18 the SiNx:H layer during the ther
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CHAPTER 2 SILICON NITRIDE LAYER FOR
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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
Page 80 and 81: 61 recombination in the SCR influen
Page 82 and 83: 63 Figure 3.13 shows that: 1) after
Page 84 and 85: CHAPTER 4 MINORITY-CARRIER LIFETIME
Page 86 and 87: 67 Figure 4.1 Α photograph of QSSP
Page 88 and 89: 69 work. The most convenient is 1 m
Page 90 and 91: 7Ι dependence of the minority carr
Page 92 and 93: 73 It was tempting to assume that l
Page 96 and 97: 77 5.2 Objective An electronic mode
Page 98 and 99: 79 Figure 5.2 is a photograph of a
Page 100 and 101: 81 impurity-gettering methods which
Page 102 and 103: 83 distribution of local currents a
Page 104 and 105: 85 modeling. Wafers were selected f
Page 106 and 107: 87 Figure 5.5 A comparison of (a) d
Page 108 and 109: 89 alloying results in metallizatio
Page 110 and 111: 91 (i) Defect clusters are the prim
Page 112 and 113: 93 SiNX induced charge density on t
Page 114 and 115: APPENDIX I PROGRAMS TO CALCULATE SR
Page 116 and 117: 97 phin = -ΕΙ - 1 / beta * log(nd
Page 118 and 119: 99 ίter3 = 0 for xi=1 to nmax/2-1
Page 120 and 121: 101 input "output file name {XXXXXX
Page 122 and 123: 103 F (i) = (exp (beta * (phip - ph
Page 124 and 125: APPENDIX III COMPUTATIONAL METHOD F
Page 126 and 127: 107 where, dscr is the width of the
Page 128 and 129: REFERENCES 1. E. Becquerel , C. R.
Page 130 and 131: 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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