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

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37 the nitride and not into the Si area thus resulting in the effectiveness of the hydrogenation from the post-deposition annealing of SiN layers to be questionable. In order to increase the sensitivity of the detection of H, Jiang and Stavola et. al. used vibrational spectroscopy, coupled with the use of Pt marker impurities in Si to probe the H that is assumed to be introduced into Si by post-deposition annealing of SiΝ :H AR coatings [74]. Their experiments indicated that hydrogenation of Si from the nitride layer yielded a modest H concentration, which is less than 10 14 cm-3 A five minute anneal at 600°C resulted in — 500 μm depth of H penetration into Si, which surprisingly suggested a H diffusion constant that is a factor only — 2 smaller than an extrapolation of the classic results of Wieringen and Warnmoltz [75]. The above approach is a promising method to introduce H into c-Si solar cells to passivate bulk defects by post-deposition annealing of H-rich SiΝ layers. However, from the studies in the literature, a thorough understanding of the mechanisms involved in hydrogen passivation is still lacking.
CHAPTER 3 MODELING OF SURFACE RECOMBINATION VELOCITY - ROLE OF THE DAMAGED LAYER 3.1 Background 3.1.1 Recombination Mechanisms in Silicon Illumination of a semiconductor junction with photons of sufficient energy creates electron-hole pairs (`generation'). Hence, the charge carrier concentration is higher under illumination than the dark (thermal equilibrium). Upon termination of illumination, the carrier concentrations return to their thermal equilibrium values. The responsible processes are called recombination. The recombination process occurs via defect levels (surface states) in the forbidden bandgap of the semiconductor. Three fundamental recombination processes are often addressed in semiconductors: —Band-to-band recombination — Trap-assisted recombination —Auger recombination. 3.1.1.1 Band-to-band Recombination. Band-to-band recombination is the inverse process to the absorption of light in a semiconductor. An electron in the conduction band falls into a non-occupied state (a hole) in the valence band; the excess energy is released in the form of a photon. Band-to-band recombination in a direct band-gap semiconductor is shown schematically in Figure 3.1 [76]. 38
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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 and 18: LIST OF FIGURES (Continued) Figure
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: 36 It was found that the bulk lifet
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 104 and 105: 85 modeling. Wafers were selected f
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87 Figure 5.5 A comparison of (a) d
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89 alloying results in metallizatio
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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
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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
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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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