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

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LIST OF FIGURES Figure Page 1.1 World solar module production 1980-2000 [ 16] 4 I.2 A schematic of photo generation effect .......................................... . ........ 5 I.3 An electrical equivalent circuit of a solar cell .......................................... 7 I.4 The I-V characteristic of a. solar cell with maximum power point [17] 8 1.5 Solar cell production and capacity [28] II 1.6 An. illustration of a. typical crystalline Si solar cell [29] 13 1.7 A pictorial representation of • various types of point, line, area and volume defects: (a) foreign interstitial; (b) dislocation; (c) self-interstitial; (d) precipitate; (e) extrinsic stacking fault and partial dislocation; (f) foreign substitutional; (g) vacancy; (h) intrinsic stacking fault surrounded by a partial dislocation; (i) foreign substitutional [30] .. 14 2.1 SEM picture of a typical texturized silicon surface using conventional NaOH texturization bath [39] 2.2 " The calculated reflectance spectra of a bare Si wafer for different surface conditions: (a) polished and (b) (I00) textured. Wafer thickness =300 μm [40] 2I 21 2.3 The calculated reflectance spectra of a Si wafer coated with SiN (n=2 and a=5.0): _double sided polished (solid line) and (I00) double sided textured (dotted line). Wafer thickness = 30 .0 μm [42] ........................................... 23 2.4 The spectrum of AM1.5 radiation [43] 24 2.5 Deposition of SiNx:H fir in (a) a direct-plasm reactor and (h) a remote-plasm reactor[50] 28 2.6 The refractive index as a function of N/Si ration for SiΝ X:H films [52] .A line is drawn through the data for visual guidance only 29 xii
LIST OF FIGURES (Continued) Figure Page 2.7 The calculated reflectance and absorbance spectra of a Si solar cell operating in air (thick lines) and in an encapsulated module (thin lines). The nonabsorbing nitride is assumed to have n=2 for air and n=2.2 for module operation [42] ..... , 31 3.I Band-to band recombination in a direct band-gap semiconductor [76] ..... , . , , . , . 39 3.2 Schematic diagram of impurity-related energy levels within the forbidden gap of a semiconductor. Levels are labeled as to whether the defect is likely to be a trap or a recombination center according to the SRH model 40 3.3 Charge distribution and band diagram at the Si-insulator interface under non-equilibrium.conditions. The non-equilibrium conditions are indicated by the separation of electron and hole quasi—Fermi levels ψ and ψ . Note the surface potential ψs is positive when the energy bands bend down ......43 3.4 Schematic diagram of a numerical algorithm for the calculation of surface recombination rates at the Si-insulator interface for given excess concentration at the edge of surface space region .[82] ................................... . ............. 46 3.5 The calculated dependence of effective SRV (Seff on the fixed positive charge density. (Q) for different interface-state densities. The results are shown for two injection levels: (a) 1014cm-3 and (b) 1016cm-3 [84] 47 3.,6 Calculated effective surface recombination velocity Seff for p-Si surface as a function of the injection level Δn in the quasi-neutral bulk for different values of interface state density Dit. Input parameters: Doping concentration = 1 x 10 16 cm-3 ; σn= 1x10-14cm2,.σp=1x10-16cm2; Qι= 1.3x10 11 cm-2 .......................... 3.7 Measured Seff(Δn) dependence at the SiΝx -passivated surfaces of three 1.5 Ω cm FZ p-Si wafers. The SiNx films were fabricated with three different PECVD methods: low-frequency(I00 kHz direct) PECVD, high-frequency (13.56 MHz) direct PECVD, and remote PECVD [56] ,. 53 3.8 Calculated dependence of Seff for n-Si and p-Si surfaces as a function of injection level (Δn) for different. wafer resistivities. D it=5x10 10 cm2 eV-1 , Q-1I0 1 . 1 cm2 54
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: LIST OF TABLES Table Page 2.1 Posit
Page 19 and 20: 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
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
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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
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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
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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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