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

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19 Chapter 4 addresses the experiments relating to the minority-carrier lifetime measurements using Quasi-Steady-State Photo-Conductance-Decay (QSSPCD) technique. The experiments indicate that wafer preparation for meaningful lifetime measurements requires a clean wafer and high quality surface passivation as well. Α novel laboratory procedure for wafer preparation is proposed. Chapter 5 is a combination of theoretical and experimental studies of defect clusters in mc-Si and their adverse effects on solar cell performance. In a typical cell, network model is employed to analyze the correlation between defect clusters and cell performance. Experimental studies of cells fabricated on wafers from the same ingot before and after firing facilitate a comparison and discussion of the impact of the defect clusters. Chapter 6 focuses on conclusions based on the above studies and some possible future directions.
CHAPTER 2 SILICON NITRIDE LAYER FOR SOLAR CELL APPLICATIONS: AN OVERVIEW 2.1 Antireflection Coating Until recently, the objective of using an antireflection coating (AR) on a solar cell has been to minimize the reflectance losses due to the cell and maximize the light trapping ability to obtain highest photocurrent for the incident solar photons. Silicon is a shiny gray material and, therefore, acts as a mirror, reflecting more than 30% of the light that is incident on it. In order to improve the conversion efficiency of a solar cell, it is necessary to minimize the amount of light reflected so that the semiconductor material can capture as much light as possible to generate charge carriers. Maximum absorbance of the incident light is preferred to achieve ideal conversion efficiency. A technique to reduce the reflectance loss is to texture the top surface. 'Chemical etching creates a pattern of cones and pyramids, which capture and trap light rays that might otherwise be deflected away from the cell. Reflected light is redirected down into the cell, where it has another chance to be absorbed. In Si solar cells, a pseudoperiodic roughness is generated by chemical etching in a NaOH or KOH-based solution. Figure 2.1 shows the surface morphology of a typical texturized silicon surface using conventional NaOH texturization bath [39]. The etching also serves to remove the surface damage produced when ingots are sawn into wafers. A rough or textured surface typically has a much lower reflectance than that of a planar surface—a feature particularly useful in the case of high refractive-index semiconductors. 20
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 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: 18 the SiNx:H layer during the ther
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 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
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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
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91 (i) Defect clusters are the prim
Page 112 and 113:
93 SiNX induced charge density on t
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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
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APPENDIX III COMPUTATIONAL METHOD F
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107 where, dscr is the width of the
Page 128 and 129:
REFERENCES 1. E. Becquerel , C. R.
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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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