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

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LIST OF FIGURES (Continued) Figure Page 3.9 Calculated dependence of surface recombination velocity (Ss) for (a) n-Si and (b) p-Si surfaces as a function of injection level (Δn) for different fixed positive charge densities and interface state densities, σn= 10 14 cm 2 and σp= 10-16 16 cm-2 56 3.10 Measured effective SRV showing dependence on excess carrier density [89] 57 3.11 High-resolution cross-sectional TEM of Si-SiΝx :Η interface before firing showing process-induced damage by plasma [92] 58 3.12 Calculated recombination velocity, components S S and SSCR (dotted lines), and the total Seff (solid lines) at SiΝx :Η/Si interface as a function of injection level. Assumptions: p-Si, 1.5 Ωcm, Q = 2x 1012cm-2, Dit1=1 x10 12 eV-1cm-2, D21x10 1 eV-1cm-2 ................... .......................................... .....e.....,. 60 3.13 A schematic illustration of Η transport from SiΝ:Η layer to bulk Si .. 62 3.14 The SIMS profiles of Η in a solar cell introduced during a PECVD SiN coating before (red line) and after contact annealing (black line) [98] ............ . ........... 63 3.15 Effect of PECVD on the internal quantum efficiency of the cell [99] ............... 64 4.1 A photograph of QSSPCD apparatus at NREL ... 67 4.2 τb of a p-type Si wafer measured by QSSPCD as a function of time. The sample was cleaned by "ICP" and passivated in IE solution. (A) after ICP; (B) dilute HF dip after (A); (C) dilute HF dip after (B); (D) after oxidation clean [108] ...... 69 4.3 Time dependence of 'Lb after including oxidation in the cleaning procedure, for sequential cleaning steps [ 108] ... ........................................ . .. . ..... . . .. 70 4.4 τb decay after light exposure (no rise time was observed) [108] 72 4.5 Short-term variation of τb fora long lifetime wafer. The wafer was cleaned with the new procedure [ 108] 72 4.6 τb of a p-type wafer, resistivity 27 Ω-cm measured after several treatments: UV for 15 min and 30 min, heating, exposure to light for different times [108] 73 xiv
LIST OF FIGURES (Continued) Figure Page 4.7 A wafer with a shallow (200-300 A) contaminated surface layer (a), after cleaning (b) and. surface passivation (c) 1108] 75 5.1 A defect map of a commercial mc-Si wafer showing clustering of defects as dark regions. The inset shows a magnified region indicated by arrows [ 112] 78 5.2 A defect cluster, region showing etches pits produced by defect etching [ 112] 79 5.3 An XTEM image of a defect cluster showing metallic precipitation [112] 80 5.4 (a) A schematic of a defect cluster, and (b) a network model of a solar cell showing voltage and current sources corresponding to dark (indicated by subscript d) _ and illuminated (indicated by subscript L) conditions, and the resistive components due to the sheet rho of the junction [ 112] 83 5.5 A comparison of (a) defect-cluster distribution in a wafer and (b) long-wavelength LBIC image of the solar cell on a sister wafer . 87 5.6 A comparison of calculated I-V characteristics of three cells—cell #113, cell #1.07, and cell having no defects [ 112] ................... . . . . ... . ... . 89 5.7 The current flow in various regions of cell #108 at different voltages [ 112] 90 xv
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: 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 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
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
Page 82 and 83:
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
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
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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
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85 modeling. Wafers were selected f
Page 106 and 107:
87 Figure 5.5 A comparison of (a) d
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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
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101 input "output file name {XXXXXX
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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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