Surface and bulk passivation of multicrystalline silicon solar cells by ...
Surface and bulk passivation of multicrystalline silicon solar cells by ... Surface and bulk passivation of multicrystalline silicon solar cells by ...
CHAPTER 1 INTRODUCTION 1.1 Solar Cells-A Perspective As the world becomes more concerned about the environmental effects of burning fossil fuels, and as fossil fuels become scarcer, we need to develop alternate energy technologies. One of the most promising is photovoltaic (PV) or solar cells that are already in use in many places. Solar photovoltaic energy conversion is a one-step conversion process which generates electrical energy from light energy. The explanation relies on ideas from quantum theory. Light is made up of packets of energy, called photons, whose energy depends on the frequency of light. The energy of photons in visible wavelengths is sufficient to excite electrons to higher energy levels where they are freer to move. Photovoltaic technology actually dates back over 160 years. The PV effect was first discovered and reported in 1839 by French physicist A.E. Becquerel [1] when he observed that certain materials would produce a small current when exposed to light. About 55 years later, in 1883, the first solar cell was built by Charles Fritts [2], an American inventor, by coating selenium wafers with an ultrathin, nearly transparent layer of gold to form a metal-semiconductor junction. Fritts's devices were very inefficient, transforming less than 1 percent of the absorbed light into electrical energy. In 1918, a Polish scientist, Jan Czochralski [3] discovered a method for monocrystalline silicon production, which enabled the production of monocrystalline silicon solar cells. In 1941, the first silicon solar cell was invented by Russell Ohl [4]. Silicon proved to be a much better semiconductor and is the predominant material that is used today in solar cells. Ohl was able to obtain energy conversions of less than one 1
2 percent; however, soon, more advances were made in order to increase PV energy conversion efficiencies. In 1954, a silicon solar cell capable of 6% energy conversion efficiency with direct sunlight was invented by three American scientists, Gerald Pearson, Calvin Fuller and Daryl Chapin [5]. They created the first solar panel by putting several strips of silicon p-n junctions together to form an array and placed it in sunlight. The first field trial of the Bell Solar Battery in actual service began on a telephone carrier system in October, 1955 [6]. The first sun-powered automobile was demonstrated in Chicago, Illinois in August 1955 [7]. In 1958, Hoffman Electronics achieved 9% efficient PV cells. Vanguard I, the first PV-powered satellite, was launched in cooperation with the U.S. Signal Corp. The satellite power system operated for eight years [7, 8]. The first telephone repeater powered by solar cells was built In Americus, Georgia [7]. In 1959, Hoffman Electronics achieved 10% efficient, commercially available PV cells. Hoffman Electronics also learned to use a grid contact, reducing the series resistance significantly [7]. On August 7 th 1959, the Explorer VI satellite was launched with a PV array of 9600 solar cells. On October 13 th 1959, Explorer VII was launched [7]. In 1960, Hoffman Electronics introduced yet another solar cell with 14% efficiency [7]. In 1963, Sharp Corporation developed the first usable photovoltaic module from silicon solar cells [9]. In 1985, researchers at the University of New South Wales in Australia constructed a solar cell with more than 20% efficiency [10]. By the late 1980s, silicon solar cells, as well as those made of gallium arsenide, with efficiencies of more than 20 % had been fabricated [11, 12]. In 1989, a concentrator solar cell, a type of device in which sunlight is concentrated onto the cell surface by means of lenses, achieved an efficiency of 37% due to the increased intensity of the collected energy [13]. In general, solar cells of widely
- 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: LIST OF FIGURES (Continued) Figure
- 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
2<br />
percent; however, soon, more advances were made in order to increase PV energy<br />
conversion efficiencies.<br />
In 1954, a <strong>silicon</strong> <strong>solar</strong> cell capable <strong>of</strong> 6% energy conversion efficiency with<br />
direct sunlight was invented <strong>by</strong> three American scientists, Gerald Pearson, Calvin<br />
Fuller <strong>and</strong> Daryl Chapin [5]. They created the first <strong>solar</strong> panel <strong>by</strong> putting several<br />
strips <strong>of</strong> <strong>silicon</strong> p-n junctions together to form an array <strong>and</strong> placed it in sunlight. The<br />
first field trial <strong>of</strong> the Bell Solar Battery in actual service began on a telephone carrier<br />
system in October, 1955 [6]. The first sun-powered automobile was demonstrated in<br />
Chicago, Illinois in August 1955 [7]. In 1958, H<strong>of</strong>fman Electronics achieved 9%<br />
efficient PV <strong>cells</strong>. Vanguard I, the first PV-powered satellite, was launched in<br />
cooperation with the U.S. Signal Corp. The satellite power system operated for eight<br />
years [7, 8]. The first telephone repeater powered <strong>by</strong> <strong>solar</strong> <strong>cells</strong> was built In<br />
Americus, Georgia [7]. In 1959, H<strong>of</strong>fman Electronics achieved 10% efficient,<br />
commercially available PV <strong>cells</strong>. H<strong>of</strong>fman Electronics also learned to use a grid<br />
contact, reducing the series resistance significantly [7]. On August 7 th 1959, the<br />
Explorer VI satellite was launched with a PV array <strong>of</strong> 9600 <strong>solar</strong> <strong>cells</strong>. On October<br />
13 th 1959, Explorer VII was launched [7]. In 1960, H<strong>of</strong>fman Electronics introduced<br />
yet another <strong>solar</strong> cell with 14% efficiency [7]. In 1963, Sharp Corporation developed<br />
the first usable photovoltaic module from <strong>silicon</strong> <strong>solar</strong> <strong>cells</strong> [9]. In 1985, researchers<br />
at the University <strong>of</strong> New South Wales in Australia constructed a <strong>solar</strong> cell with more<br />
than 20% efficiency [10]. By the late 1980s, <strong>silicon</strong> <strong>solar</strong> <strong>cells</strong>, as well as those made<br />
<strong>of</strong> gallium arsenide, with efficiencies <strong>of</strong> more than 20 % had been fabricated [11, 12].<br />
In 1989, a concentrator <strong>solar</strong> cell, a type <strong>of</strong> device in which sunlight is concentrated<br />
onto the cell surface <strong>by</strong> means <strong>of</strong> lenses, achieved an efficiency <strong>of</strong> 37% due to the<br />
increased intensity <strong>of</strong> the collected energy [13]. In general, <strong>solar</strong> <strong>cells</strong> <strong>of</strong> widely
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