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

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59 carrier recombination within the damaged layer, which occurs within the SCR. Based on this, one must include recombination in the SCR. Α similar conclusion was arrived at by Schmidt [93], but his reasoning did not include the surface damage. However, one can follow his approach to calculate the effect of increased recombination near the damaged surface. Once SCR exists beneath the surface of the wafer, its detailed characteristics are uniquely determined by the shape of the potential barrier. Α full derivation of approximate solutions to the recombination velocity in SCR can be found in the literature [94, 95]. The surface potential distribution across the space charge region is given by: ψ(z) =ψS •e -z/L, where, z is the vertical distance from the surface, and Ys is the surface potential at the surface or at one end of SCR ( z = 0 ), which can be found by an iterative approach of Shockley-Read-Hall (SRH) formalism. L is the extrinsic Debye length and is defined as: where, nb, pb denote carrier density of electrons and holes in the bulk, respectively, and εb is the dielectric constant of the semiconductor. In the SCR, the carrier densities are functions of the position z: n(z) = n b eβψ, p(z) = pbeβψ The definition and parameterization of recombination rate in the SCR, USCR(z) parameterization can be found in the literature [96]. The recombination velocity in the SCR is calculated by:
SSCR S + = eff S 60 1 SSCR = Δη U scn (z)dz Hence, the effective SRV is given by: A modified SRV model calculation is proposed based on current SRH formalism and recombination in SCR. Figure 3.12 shows the calculated results for Seff as a function of injection level. Seff1 (when there is a damaged layer) has a more pronounced injection-level dependence compared to Seff2 (when there is no damage layer). SSCR1 and SSCR2 denote the intrinsic recombination in the SCR, with or without the damaged layer, respectively. S s is the recombination at the surface. Figure 3.12 also demonstrates this at low injection levels; Figure 3.12 Calculated recombination velocity components . S S and SSCR (dotted lines), and the total Seff (solid lines) at SiΝ :H/Si interface as a function of injection level. Assumptions: p-Si, 1.5 Ω-cm, Q= 2x 1012cm-2, Di t1 =1 x 10 , 12 eV-1cm2 D12=1x10 11 eV -1cm-2 .
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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
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 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 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
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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
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90. B.L. Sopori, Y. Zhang, and N.M.
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