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

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85 modeling. Wafers were selected from different regions of a mc-Si casting and separated into two "sister" groups of adjacent wafers. Wafers from one group were defect-mapped using a commercial machine, GT-PVSCAN 5000, to determine distributions of defect clusters, and C and Ο measurements were performed [110]. These distributions were simplified in order to convert this information into easily useable distributions of the defect clusters for the Network model. As an example, Figure 5.5(a) shows a sketch of defect clusters obtained from the defect maps for a wafer. These distributions were also compared with the LBIC maps after fabricating cells on sister wafers. Figure 5.5(b) shows the long-wavelength LBIC response of the cell fabricated on the sister wafer of Figure 5.5(a). A pattern similar to the defect pattern of Figure 5.5(a) can be seen in the LBIC map. The LBIC map also shows ratio of Jph in defect cluster and defect-free regions. A comparison of maps in Figures 5(a) and (b) shows important distinctions. First, it is clear that the LBIC map (compared to defect map) exhibits additional defects in the bulk of the cell. However, these additional defects have densities below the cut-off for a defect cluster. The second feature is that the defect clusters in the LBIC map appear to be "thinned" compared to the defect map. These are the results of a lower resolution for the PVSCAN in a defect-mapping mode as compared to the LBIC mode. The third feature seen in the LBIC map is square patterns of low photoresponse; these correspond to Ag pads on the back of the cell that are used for making solder contacts to the backside of the cell. These pads appear in the LBIC image because (a) the cell has a long minority-carrier diffusion length, and (b) the back Ag-Si contact has a higher recombination compared to rest of the back contact.
86 The defect-clustered regions were TEM analyzed to determine the nature of the precipitations. The precipitates contain a multitude of impurities such as Fe, Cr, C, and O. All solar cells were characterized for their I- V characteristics and LBIC maps. The LBIC map identifies J ph values in defect and defect-free regions.
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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
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24 information is application-orien
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26 film fed growth (EFG) ribbon sil
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28 Figure 2.5 Deposition of SiΝ :
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30 Figure 2.6 shows the dependence
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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 94 and 95: 75 resistivities and lifetime) do n
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 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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