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

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7Ι dependence of the minority carrier lifetime, using I-Ε passivation. This curve shows that the lifetime maximum was reached much faster and the maximum is higher than previous values. It is clear that it is necessary to remove the native oxide surface (in this case by oxidation and dilute HF dip). In order to determine the depth of the native oxide surface, oxidation was performed in steps. Figure 4.3 shows the time dependence of the lifetime measurements for first three steps. The sample was cleaned and oxidized after each set of measurements. Further oxidation only increased the slope of the curves while the τmax remained the same. 4.2.3 Influence of Illumination It was also observed that, if the measurements were performed at shorter intervals, the slope of the curves increased. This is an interesting phenomenon indicating that the I-Ε surface passivation has a light-activated component. To evaluate this effect, a wafer was cleaned (using the new oxidation procedure), placed in an I-Ε bag, and exposed to about 0.5 sun intensity from a solar simulator for 15 minutes. It was found that the lifetime after exposure to light yielded Τmax immediately after the exposure; furthermore, there was a slow decrease (as shown in Figure 4.4) in τ. This decrease occurs for all wafers after the measured lifetime reaches a maximum. Figure 4.5 shows a short-term variation of τb for a long lifetime wafer.
72 Figure 4.4 τb decay after light exposure (no rise time was observed) [108]. Figure 4.5 Short-term variation of τb for a long lifetime wafer. The wafer was cleaned with the new procedure [108].
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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
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 and 30:
10 First generation cells consist o
Page 31 and 32:
12 Basically, materials for manufac
Page 33 and 34:
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
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
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 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 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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