WO2013036098A1 - A solar cell and method of fabricating thereof - Google Patents

A solar cell and method of fabricating thereof Download PDF

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Publication number
WO2013036098A1
WO2013036098A1 PCT/MY2012/000165 MY2012000165W WO2013036098A1 WO 2013036098 A1 WO2013036098 A1 WO 2013036098A1 MY 2012000165 W MY2012000165 W MY 2012000165W WO 2013036098 A1 WO2013036098 A1 WO 2013036098A1
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WIPO (PCT)
Prior art keywords
solar cell
layer
substrate
absorption
nano
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PCT/MY2012/000165
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French (fr)
Inventor
Witjaksono Gunawan
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Mimos Berhad
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Publication of WO2013036098A1 publication Critical patent/WO2013036098A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/0352—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
    • H01L31/035209—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions comprising a quantum structures
    • H01L31/035218—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions comprising a quantum structures the quantum structure being quantum dots
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
    • H01L31/0352—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/054—Optical elements directly associated or integrated with the PV cell, e.g. light-reflecting means or light-concentrating means
    • H01L31/0549—Optical elements directly associated or integrated with the PV cell, e.g. light-reflecting means or light-concentrating means comprising spectrum splitting means, e.g. dichroic mirrors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/52—PV systems with concentrators

Definitions

  • the present invention relates to a solar cell and more particularly to a solar cell capable of absorbing multi-wavelength light for converting to electrical energy.
  • the photovoltaic cell has an active silicon (Si) or silicon-germanium (SiGe) substrate subcell having an active upper side and characterized by a substrate bandgap.
  • One or more upper subcells are disposed adjacent the upper side and current matched with the substrate subcell, with the upper subcell(s) typically having bandgap(s) greater than the substrate bandgap.
  • a transition layer may be placed intermediate the upper side and the upper subcell(s).
  • US Patent No. 4,332,974 which relates to a multi-junction photovoltaic solar cell for use with a concentrating lens.
  • the cell comprises an elemental single crystal substrate without an internal light sensitive junction, upon which are two or more successive homogenous layers of semiconductor material, each layer containing within it a light sensitive p/n junction of a similar polarity, each layer having essentially the same lattice constant as the single crystal substrate, each layer having a shorting junction contact with the layer immediately above and below it, each successive layer adsorbing light energy at a shorter wavelength, and each layer being of sufficient thickness and appropriate composition to develop essentially the same current as the other layers.
  • the outer surfaces of the top layer and the substrate are provided with electrical contacts for distribution of the electric current.
  • the top contact comprises a layer of a transparent conductive material with electrical connections and the whole structure is completed with an antireflection coating over the top.
  • all layers must have matching crystal or lattice structures to avoid defects or dislocations in the lattice. Mismatching of the lattice causes loss of photo-generated minority carriers and significantly degrades the photovoltaic quality of the multi-junction solar cell.
  • the multi-junction solar cell requires integration of concentrating mirrors or lenses to allow more concentrated light to penetrate deeper for the absorption of photons for the lower stacked active layers.
  • US 2010/0037935 which relates to a solar cell module.
  • the module includes a housing with a first side and an opposing spaced-apart second side.
  • a plurality of lenses may be positioned on the first side of the housing, and a plurality of solar cell receivers may be positioned on the second side of the housing.
  • Each of the plurality of solar cell receivers may include a lll-V compound semiconductor multifunction solar cell.
  • Each may also include a bypass diode coupled with the solar cell.
  • At least one optical element may be positioned above the solar cell to guide the light from one of the lenses onto the solar cell.
  • Each of said solar cell receivers may be disposed in an optical path of one of the lenses.
  • the lens and the at least one optical element may concentrate the light onto the respective solar cell by a factor of 1000 or more to generate in excess of 25 watts of peak power.
  • Another effort to improve the efficiency of a solar cell is provided in PCT Application No. PCT/US2006/007290 which relates to a photovoltaic device.
  • the photovoltaic device includes a first energy absorbing surface and a second energy absorbing being substantially parallel to the first energy absorbing surface.
  • the photovoltaic device may include a third energy absorbing surface being substantially perpendicular to the first energy absorbing surface and the second energy absorbing surface.
  • Each of the first energy absorbing surface, the second energy absorbing surface, and the third energy absorbing surface may be configured to convert energy from photons into electrical energy.
  • the photons may be impinging one or more of the first energy absorbing surface, the second energy absorbing surface, and the third energy absorbing surface.
  • the first, second, and the third energy absorbing surfaces may be oriented in manner to cause the photons to bounce between two or more of the first energy absorbing surface, the second energy absorbing surface, and the third energy absorbing surface.
  • the photovoltaic device poses a few drawbacks.
  • MBE Molecular Beam Epitaxy
  • the structure needs to be grown by Molecular Beam Epitaxy (MBE) and thus, increases the complexity of fabricating such device.
  • the light confinement is merely based on reflection which can easily be loss.
  • a solar cell (100) which comprises of a substrate (110), an absorption layer (120) disposed on the substrate (110), a top contact (130) disposed on a portion of a top surface of the absorption layer (120), and a bottom contact (140) is disposed on a portion of a bottom surface of the substrate (110).
  • the solar cell (100) is characterised in that the absorption layer (120) is laterally divided into at least two absorption regions (121), wherein each absorption region (121) is made of different nanostructured materials having different bandgaps.
  • the absorption layer (120) is made of either cadmium selenide (CdSe), zinc oxide (ZnO), zinc sulfide (ZnS), cadmium sulphide (CdS), cadmium telluride (CdTe) or lead selenide (PbSe).
  • the solar cell (100) further includes a coating layer disposed on the absorption layer (120) and the top contact (130). Moreover, the coating layer suitably includes a splitting wavelength layer.
  • a solar cell (200) which comprises of a substrate (210), an absorption layer (220) disposed on the substrate (210), a top contact (230) disposed on a portion of a top surface of the absorption layer (220), a bottom contact (240) is disposed on a portion of a bottom surface of the substrate (210).
  • the solar cell (200) is characterised in that the absorption layer (220) is laterally divided into at least two absorption regions (221), wherein each absorption region (221) has a particular nano-particle radius size to absorb a particular spectrum of light.
  • the absorption layer (220) is made of either cadmium selenide (CdSe), zinc oxide (ZnO), zinc sulfide (ZnS), cadmium sulphide (CdS), cadmium telluride (CdTe) or lead selenide (PbSe).
  • CdSe cadmium selenide
  • ZnO zinc oxide
  • ZnS zinc sulfide
  • ZnS zinc sulfide
  • CdS cadmium sulphide
  • CdTe cadmium telluride
  • PbSe lead selenide
  • the solar cell (200) further includes a coating layer (250) disposed on the absorption layer (220).
  • the coating layer (250) suitably includes a splitting wavelength layer.
  • a method of fabricating a solar cell (200) comprises the steps of (a) preparing a substrate (210); (b) spin coating and patterning a photoresist layer (310) on the substrate; (c) curing the photoresist layer (310); (d) mixing a nano-particle material having a certain nano- particle radius size with a binder; (e) spin coating the nano-particle mixture (320) on the substrate (210) and the photoresist layer (310); (f) removing the photoresist layer (310) through a lift-off process; (g) functionalizing the binder in the nano-particle mixture (320); (h) repeating steps (b) to (g) until a desired number of absorption regions (221) having varying nano-particle radius size have been deposited on the substrate (210); (i) etching a portion of the top surface of the nano-particle mixtures (320) to remove the binder of the nano-particle mixtures (320); and
  • Figure 1 shows a solar cell (100) according to a first embodiment of the present invention.
  • FIG 2 shows a solar cell (200) according to a second embodiment of the present invention.
  • Figure 3 shows the solar cell (200) of Figure 2 having a coating layer (250) disposed on an absorption layer (220).
  • Figure 4 shows a flowchart of fabricating the solar cell (200) of Figure 2.
  • Figures 5 (a-f) show a method of fabricating the solar cell (200) of Figure 2.
  • the solar cell (100) is capable of absorbing multiple spectrums of light to convert the spectrums of light to electrical energy.
  • the solar cell (100) comprises of a substrate (110), an absorption layer (120), a top contact (130), and a bottom contact (140).
  • the solar cell (100) may either be an n-p junction device or a p-n junction device.
  • the substrate ( 10) is doped with a p-type dopant and the absorption layer (120) is doped with an n-type dopant.
  • the substrate (110) is doped with an n-type dopant and the absorption layer (120) is doped with a p-type dopant.
  • the absorption layer (120) is disposed on the substrate (110).
  • the absorption layer (120) is laterally divided into multiple absorption regions (121), wherein each absorption region (121) is made of different nanostructured materials having different bandgaps such as but not limited to cadmium selenide (CdSe), zinc oxide (ZnO), zinc sulfide (ZnS), cadmium sulphide (CdS), cadmium telluride (CdTe) and lead selenide (PbSe).
  • each absorption region (121) absorbs different spectrums of light.
  • a first absorption region (121a) is made of CdS with a bandgap of 2.4 eV with center absorption wavelength at 450 nm
  • a second absorption region (121b) is made of ZnS with a bandgap of 3.7 eV with center absorption wavelength at 470 nm
  • a third absorption region (121c) is made of ZnO with a bandgap of 3.3 eV with center absorption wavelength at 397 nm.
  • the top and bottom contacts (130, 140) are used to conduct electrons due to the absorption of photons from light.
  • the top and bottom contacts (130, 140) are connected to an external load to supply the electrical energy generated.
  • the top contact (130) is disposed on a portion of a top surface of the absorption layer (120). Moreover, the top contact (130) extends on the top surface of each absorption region (121) and thus, the top contact (130) is able to accumulate the electrical energy generated from each absorption region (121).
  • the bottom contact (140) is disposed on a portion of a bottom surface of the substrate (110).
  • the solar cell (100) further includes a coating layer disposed on the absorption layer (120) and the top contact (130).
  • the coating layer provides mechanical strength to the nano-structured absorption layer (120).
  • the coating layer acts as an anti-reflection to allow the transmission of all light spectrums to the absorption layer (120).
  • the coating layer includes a splitting wavelength layer to spread the light according to its wavelength and directs the light according to its bandwidth to the respective absorption regions ( 21).
  • FIG 2 there is shown a solar cell (200) according to a second embodiment of the present invention.
  • the solar cell (200) is capable of absorbing multiple spectrums of light to convert the spectrums of light to electrical energy.
  • the solar cell (200) comprises of a substrate (210), an absorption layer (220), a top contact (230), and a bottom contact (240).
  • the solar cell (200) may either be an n-p junction device or a p-n junction device.
  • the substrate (210) is doped with a p-type dopant and the absorption layer (220) is doped with an n-type dopant.
  • the substrate (210) is doped with an n-type dopant and the absorption layer (220) is doped with a p-type dopant.
  • the absorption layer (220) is disposed on the substrate (210) and it is suitably made of nanostructured material such as, but not limited to cadmium selenide (CdSe), zinc oxide (ZnO), zinc sulfide (ZnS), cadmium sulphide (CdS), cadmium telluride (CdTe) and lead selenide (PbSe).
  • the nanostructured material demonstrates modified optical and electronic properties due to its three dimensional confinement of the electrons and holes. Most notably, the energy levels in the conduction and valence bands become discreet. These properties vary as functions of the degree of confinement and therefore, as functions of the nanostructure size. As the confinement increases, so does the energy difference between the valence and conduction bands.
  • the absorption layer (220) is laterally divided into multiple absorption regions (221), wherein each absorption region (221) has a particular nano-particle radius size to absorb a particular spectrum of light.
  • Each absorption region (221) has different bandgaps depending on its nano-particle radius size which is determined by the equation below.
  • R is the nanoparticle radius
  • e is the elementary charge
  • ft is reduced plank constant
  • ⁇ is the bulk dielectric constant
  • m* e and m* h are the effective masses of the electrons and holes respectively.
  • the top and bottom contacts (230, 240) are used to conduct electrons due to the absorption of photons from light.
  • the top and bottom contacts (230, 240) are connected to an external load to supply the electrical energy generated.
  • the top contact (230) is disposed on a portion of a top surface of the absorption layer (220). Moreover, the top contact (230) extends on the top surface of each absorption region (221) and thus, the top contact (230) is able to accumulate the electrical energy generated from each absorption region (221).
  • the bottom contact (240) is disposed on a portion of a bottom surface of the substrate (210).
  • the solar cell (200) further includes a coating layer (250) disposed on the absorption layer (220) and the top contact (230).
  • the coating layer (250) provides mechanical strength to the nano-structured absorption layer (220).
  • the coating layer (250) acts as an anti-reflection to allow the transmission of all light spectrums to the absorption layer (220).
  • the coating layer (250) further includes a splitting wavelength layer to spread the light according to its wavelength and directs the light according to its bandwidth to corresponding regions of the absorption layer (220).
  • Figure 3 shows the solar cell (200) having a coating layer (250) disposed on the absorption layer (220) and the top contact (230).
  • a substrate (210) is prepared as shown in Figure 5a.
  • a photoresist layer (310) is spin coated on the substrate (210).
  • the photoresist layer (310) is then patterned through a lithography process to define a first region of the absorption layer (220) as shown in Figure 5b.
  • the patterned photoresist layer (310) is cured through either thermal curing or ultraviolet light curing.
  • a nano-particle material of a certain nano-particle radius size is mixed with a binder. This is to ensure that nano-particle material is maintained in the binder and to enhance the adhesion to the substrate (210).
  • the nano-particle mixture (320) is spin coated on the substrate (210) and the photoresist layer (310) as in step 405.
  • Figure 5c shows the nano-particle mixture (320) disposed on the substrate (210) and the photoresist layer (310).
  • photoresist layer (310) is removed through a lift-off process. Thus, this removes the nano-particle mixture (320) disposed on the photoresist layer (310) as shown in Figure 5d
  • the binder in the nano-particle mixture (320) is functionalized to provide a good adhesion of the nano-particle material in the nano- particle mixture (320) to the substrate (210).
  • Steps 402 to 407 are repeated accordingly for a nano-particle material having different nano-particle radius size.
  • the steps are repeated until the desired number of absorption regions (221) having varying nano-particle radius size have been deposited on the substrate (210) (decision 408).
  • nano-particle material having varying nano-particle radius size is disposed on the substrate (210) which forms the absorption layer (220) as shown in Figure 5e.
  • a portion of the top surface of the nano-particle mixtures (320) is etched to remove the binder and thus, exposing the nano-particle material.
  • the exposed nano-particle material is disposed with a conductor layer (330) on top of it as shown in Figure 5f (step 410).
  • the conductor layer (330) forms the top contact (230) of the solar cell (200).
  • the direct contact of the exposed nano-particle material with the conductor layer (330) allows the transfer of electron efficiently for converting light to electricity.
  • the solar cell can either be a p-n junction device or an n-p junction device, it is apparent to a person skilled in the art that the solar cell can be designed as a p-i-n junction device or a n-i-p junction device. While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrated and describe all possible forms of the invention. Rather, the words used in the specifications are words of description rather than limitation and various changes may be made without departing from the scope of the invention.

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  • Condensed Matter Physics & Semiconductors (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
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Abstract

The present invention relates to a solar cell capable of absorbing multiple spectrums of light to convert the spectrums of light to electrical energy. The solar cell (100, 200) comprises of a substrate (110, 210), an absorption layer (120, 220), a top contact (130, 230), a bottom contact (140, 240). The absorption layer (120, 220) is laterally divided into at least two absorption regions (121, 221), wherein each absorption region (121, 221) has different bandgaps.

Description

A SOLAR CELL AND METHOD OF FABRICATING THEREOF
FIELD OF INVENTION
The present invention relates to a solar cell and more particularly to a solar cell capable of absorbing multi-wavelength light for converting to electrical energy.
BACKGROUND OF THE INVENTION
The interest of solar cell continues to increase as an alternative source of energy and a way to reduce concerns over pollution. The continued interest has been both in terrestrial and non-terrestrial applications. In the terrestrial applications, the cost per watt of electrical power generated by a solar cell is the main factor inhibits their widespread use. Conversion efficiency of sunlight to electricity is of critical importance for terrestrial photovoltaic systems for given required power output of the system. Meanwhile, in the non-terrestrial environment of outer space, the concern of limited resources in the outer-space vehicle has put requirement of high efficiency on solar cell.
Irrespective of the applications, and as with any energy generation system, a lot of efforts have been done to increase the efficiency output of a solar cell device. Such efforts include the development of a multi-junction solar cell, wherein multiple active layers having different energy bandgaps are stacked vertically or transversely so that each active layer can absorb a different part of wide energy spectrum of photons in sunlight.
An example of the multi-junction solar cell is provided in US Patent No. 6,340,788 which relates to an improved photovoltaic cell. The photovoltaic cell has an active silicon (Si) or silicon-germanium (SiGe) substrate subcell having an active upper side and characterized by a substrate bandgap. One or more upper subcells are disposed adjacent the upper side and current matched with the substrate subcell, with the upper subcell(s) typically having bandgap(s) greater than the substrate bandgap. A transition layer may be placed intermediate the upper side and the upper subcell(s).
Another example of the multi-junction solar cell is provided in US Patent No. 4,332,974 which relates to a multi-junction photovoltaic solar cell for use with a concentrating lens. The cell comprises an elemental single crystal substrate without an internal light sensitive junction, upon which are two or more successive homogenous layers of semiconductor material, each layer containing within it a light sensitive p/n junction of a similar polarity, each layer having essentially the same lattice constant as the single crystal substrate, each layer having a shorting junction contact with the layer immediately above and below it, each successive layer adsorbing light energy at a shorter wavelength, and each layer being of sufficient thickness and appropriate composition to develop essentially the same current as the other layers. The outer surfaces of the top layer and the substrate are provided with electrical contacts for distribution of the electric current. The top contact comprises a layer of a transparent conductive material with electrical connections and the whole structure is completed with an antireflection coating over the top. As the active layers stacked on top of one another, all layers must have matching crystal or lattice structures to avoid defects or dislocations in the lattice. Mismatching of the lattice causes loss of photo-generated minority carriers and significantly degrades the photovoltaic quality of the multi-junction solar cell. Moreover, the multi-junction solar cell requires integration of concentrating mirrors or lenses to allow more concentrated light to penetrate deeper for the absorption of photons for the lower stacked active layers.
An example of a multi-junction solar cell integrated with lenses is provided in US 2010/0037935 which relates to a solar cell module. The module includes a housing with a first side and an opposing spaced-apart second side. A plurality of lenses may be positioned on the first side of the housing, and a plurality of solar cell receivers may be positioned on the second side of the housing. Each of the plurality of solar cell receivers may include a lll-V compound semiconductor multifunction solar cell. Each may also include a bypass diode coupled with the solar cell. At least one optical element may be positioned above the solar cell to guide the light from one of the lenses onto the solar cell. Each of said solar cell receivers may be disposed in an optical path of one of the lenses. The lens and the at least one optical element may concentrate the light onto the respective solar cell by a factor of 1000 or more to generate in excess of 25 watts of peak power. Another effort to improve the efficiency of a solar cell is provided in PCT Application No. PCT/US2006/007290 which relates to a photovoltaic device. The photovoltaic device includes a first energy absorbing surface and a second energy absorbing being substantially parallel to the first energy absorbing surface. The photovoltaic device may include a third energy absorbing surface being substantially perpendicular to the first energy absorbing surface and the second energy absorbing surface. Each of the first energy absorbing surface, the second energy absorbing surface, and the third energy absorbing surface may be configured to convert energy from photons into electrical energy. The photons may be impinging one or more of the first energy absorbing surface, the second energy absorbing surface, and the third energy absorbing surface. The first, second, and the third energy absorbing surfaces may be oriented in manner to cause the photons to bounce between two or more of the first energy absorbing surface, the second energy absorbing surface, and the third energy absorbing surface.
However, the photovoltaic device poses a few drawbacks. To fabricate the photovoltaic device, the structure needs to be grown by Molecular Beam Epitaxy (MBE) and thus, increases the complexity of fabricating such device. Moreover, the light confinement is merely based on reflection which can easily be loss.
Therefore, there is a need to provide a solar cell that addresses the aforementioned drawbacks. SUMMARY OF INVENTION
The present invention provides a solar cell and a method of fabricating the solar cell. In one aspect of the invention, a solar cell (100) is provided which comprises of a substrate (110), an absorption layer (120) disposed on the substrate (110), a top contact (130) disposed on a portion of a top surface of the absorption layer (120), and a bottom contact (140) is disposed on a portion of a bottom surface of the substrate (110). Moreover, the solar cell (100) is characterised in that the absorption layer (120) is laterally divided into at least two absorption regions (121), wherein each absorption region (121) is made of different nanostructured materials having different bandgaps. Preferably, the absorption layer (120) is made of either cadmium selenide (CdSe), zinc oxide (ZnO), zinc sulfide (ZnS), cadmium sulphide (CdS), cadmium telluride (CdTe) or lead selenide (PbSe). Preferably, the solar cell (100) further includes a coating layer disposed on the absorption layer (120) and the top contact (130). Moreover, the coating layer suitably includes a splitting wavelength layer.
In another aspect of the invention, a solar cell (200) is provided which comprises of a substrate (210), an absorption layer (220) disposed on the substrate (210), a top contact (230) disposed on a portion of a top surface of the absorption layer (220), a bottom contact (240) is disposed on a portion of a bottom surface of the substrate (210). Moreover, the solar cell (200) is characterised in that the absorption layer (220) is laterally divided into at least two absorption regions (221), wherein each absorption region (221) has a particular nano-particle radius size to absorb a particular spectrum of light.
Preferably, the absorption layer (220) is made of either cadmium selenide (CdSe), zinc oxide (ZnO), zinc sulfide (ZnS), cadmium sulphide (CdS), cadmium telluride (CdTe) or lead selenide (PbSe).
Preferably, the solar cell (200) further includes a coating layer (250) disposed on the absorption layer (220). Moreover, the coating layer (250) suitably includes a splitting wavelength layer.
In yet another aspect of the invention, a method of fabricating a solar cell (200) is provided. The method comprises the steps of (a) preparing a substrate (210); (b) spin coating and patterning a photoresist layer (310) on the substrate; (c) curing the photoresist layer (310); (d) mixing a nano-particle material having a certain nano- particle radius size with a binder; (e) spin coating the nano-particle mixture (320) on the substrate (210) and the photoresist layer (310); (f) removing the photoresist layer (310) through a lift-off process; (g) functionalizing the binder in the nano-particle mixture (320); (h) repeating steps (b) to (g) until a desired number of absorption regions (221) having varying nano-particle radius size have been deposited on the substrate (210); (i) etching a portion of the top surface of the nano-particle mixtures (320) to remove the binder of the nano-particle mixtures (320); and (j) depositing a conductor layer (330) on the etched portion of the nano-particle mixtures (320).
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
Figure 1 shows a solar cell (100) according to a first embodiment of the present invention.
Figure 2 shows a solar cell (200) according to a second embodiment of the present invention. Figure 3 shows the solar cell (200) of Figure 2 having a coating layer (250) disposed on an absorption layer (220).
Figure 4 shows a flowchart of fabricating the solar cell (200) of Figure 2. Figures 5 (a-f) show a method of fabricating the solar cell (200) of Figure 2.
DESCRIPTION OF THE PREFFERED EMBODIMENT
A preferred embodiment of the present invention will be described herein below with reference to the accompanying drawings. In the following description, well known functions or constructions are not described in detail since they would obscure the description with unnecessary detail.
Referring now to Figure 1 , there is shown a solar cell (100) according to a first embodiment of the present invention. The solar cell (100) is capable of absorbing multiple spectrums of light to convert the spectrums of light to electrical energy. The solar cell (100) comprises of a substrate (110), an absorption layer (120), a top contact (130), and a bottom contact (140). The solar cell (100) may either be an n-p junction device or a p-n junction device. For an n-p junction device, the substrate ( 10) is doped with a p-type dopant and the absorption layer (120) is doped with an n-type dopant. For a p-n junction device, the substrate (110) is doped with an n-type dopant and the absorption layer (120) is doped with a p-type dopant.
The absorption layer (120) is disposed on the substrate (110). The absorption layer (120) is laterally divided into multiple absorption regions (121), wherein each absorption region (121) is made of different nanostructured materials having different bandgaps such as but not limited to cadmium selenide (CdSe), zinc oxide (ZnO), zinc sulfide (ZnS), cadmium sulphide (CdS), cadmium telluride (CdTe) and lead selenide (PbSe). Thus, each absorption region (121) absorbs different spectrums of light. For instance, a first absorption region (121a) is made of CdS with a bandgap of 2.4 eV with center absorption wavelength at 450 nm, a second absorption region (121b) is made of ZnS with a bandgap of 3.7 eV with center absorption wavelength at 470 nm, and a third absorption region (121c) is made of ZnO with a bandgap of 3.3 eV with center absorption wavelength at 397 nm. By having each absorption region (121) absorbing only a particular spectrum of light, it reduces the heat created due to suppression of phonon generation and as a result, it increases the quantum efficiency of the absorption layer (120).
The top and bottom contacts (130, 140) are used to conduct electrons due to the absorption of photons from light. The top and bottom contacts (130, 140) are connected to an external load to supply the electrical energy generated. The top contact (130) is disposed on a portion of a top surface of the absorption layer (120). Moreover, the top contact (130) extends on the top surface of each absorption region (121) and thus, the top contact (130) is able to accumulate the electrical energy generated from each absorption region (121). The bottom contact (140) is disposed on a portion of a bottom surface of the substrate (110).
Preferably, the solar cell (100) further includes a coating layer disposed on the absorption layer (120) and the top contact (130). The coating layer provides mechanical strength to the nano-structured absorption layer (120). Moreover, the coating layer acts as an anti-reflection to allow the transmission of all light spectrums to the absorption layer (120). Preferably, the coating layer includes a splitting wavelength layer to spread the light according to its wavelength and directs the light according to its bandwidth to the respective absorption regions ( 21). Referring now to Figure 2, there is shown a solar cell (200) according to a second embodiment of the present invention. The solar cell (200) is capable of absorbing multiple spectrums of light to convert the spectrums of light to electrical energy. The solar cell (200) comprises of a substrate (210), an absorption layer (220), a top contact (230), and a bottom contact (240). The solar cell (200) may either be an n-p junction device or a p-n junction device. For an n-p junction device, the substrate (210) is doped with a p-type dopant and the absorption layer (220) is doped with an n-type dopant. For a p-n junction device, the substrate (210) is doped with an n-type dopant and the absorption layer (220) is doped with a p-type dopant.
The absorption layer (220) is disposed on the substrate (210) and it is suitably made of nanostructured material such as, but not limited to cadmium selenide (CdSe), zinc oxide (ZnO), zinc sulfide (ZnS), cadmium sulphide (CdS), cadmium telluride (CdTe) and lead selenide (PbSe). The nanostructured material demonstrates modified optical and electronic properties due to its three dimensional confinement of the electrons and holes. Most notably, the energy levels in the conduction and valence bands become discreet. These properties vary as functions of the degree of confinement and therefore, as functions of the nanostructure size. As the confinement increases, so does the energy difference between the valence and conduction bands. In regard to this, the absorption layer (220) is laterally divided into multiple absorption regions (221), wherein each absorption region (221) has a particular nano-particle radius size to absorb a particular spectrum of light. Each absorption region (221) has different bandgaps depending on its nano-particle radius size which is determined by the equation below.
Figure imgf000008_0001
where R is the nanoparticle radius, e is the elementary charge, ft is reduced plank constant, ε is the bulk dielectric constant, and m*e and m*h are the effective masses of the electrons and holes respectively.
The top and bottom contacts (230, 240) are used to conduct electrons due to the absorption of photons from light. The top and bottom contacts (230, 240) are connected to an external load to supply the electrical energy generated. The top contact (230) is disposed on a portion of a top surface of the absorption layer (220). Moreover, the top contact (230) extends on the top surface of each absorption region (221) and thus, the top contact (230) is able to accumulate the electrical energy generated from each absorption region (221). The bottom contact (240) is disposed on a portion of a bottom surface of the substrate (210).
Preferably, the solar cell (200) further includes a coating layer (250) disposed on the absorption layer (220) and the top contact (230). The coating layer (250) provides mechanical strength to the nano-structured absorption layer (220). Moreover, the coating layer (250) acts as an anti-reflection to allow the transmission of all light spectrums to the absorption layer (220). Preferably, the coating layer (250) further includes a splitting wavelength layer to spread the light according to its wavelength and directs the light according to its bandwidth to corresponding regions of the absorption layer (220). Figure 3 shows the solar cell (200) having a coating layer (250) disposed on the absorption layer (220) and the top contact (230).
Referring now to Figure 4, there is provided a method of fabricating the solar cell (200) of Figure 2. Initially, as in step 401 , a substrate (210) is prepared as shown in Figure 5a. In step 402, a photoresist layer (310) is spin coated on the substrate (210). The photoresist layer (310) is then patterned through a lithography process to define a first region of the absorption layer (220) as shown in Figure 5b. Next, as in step 403, the patterned photoresist layer (310) is cured through either thermal curing or ultraviolet light curing. In step 404, a nano-particle material of a certain nano-particle radius size is mixed with a binder. This is to ensure that nano-particle material is maintained in the binder and to enhance the adhesion to the substrate (210).
Thereon, the nano-particle mixture (320) is spin coated on the substrate (210) and the photoresist layer (310) as in step 405. Figure 5c shows the nano-particle mixture (320) disposed on the substrate (210) and the photoresist layer (310). In step 406, photoresist layer (310) is removed through a lift-off process. Thus, this removes the nano-particle mixture (320) disposed on the photoresist layer (310) as shown in Figure 5d Next, as in step 407, the binder in the nano-particle mixture (320) is functionalized to provide a good adhesion of the nano-particle material in the nano- particle mixture (320) to the substrate (210). Steps 402 to 407 are repeated accordingly for a nano-particle material having different nano-particle radius size. The steps are repeated until the desired number of absorption regions (221) having varying nano-particle radius size have been deposited on the substrate (210) (decision 408). As a result, nano-particle material having varying nano-particle radius size is disposed on the substrate (210) which forms the absorption layer (220) as shown in Figure 5e.
Thereon, as in step 409, a portion of the top surface of the nano-particle mixtures (320) is etched to remove the binder and thus, exposing the nano-particle material. The exposed nano-particle material is disposed with a conductor layer (330) on top of it as shown in Figure 5f (step 410). The conductor layer (330) forms the top contact (230) of the solar cell (200). The direct contact of the exposed nano-particle material with the conductor layer (330) allows the transfer of electron efficiently for converting light to electricity. Although described in the description that the solar cell can either be a p-n junction device or an n-p junction device, it is apparent to a person skilled in the art that the solar cell can be designed as a p-i-n junction device or a n-i-p junction device. While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrated and describe all possible forms of the invention. Rather, the words used in the specifications are words of description rather than limitation and various changes may be made without departing from the scope of the invention.

Claims

1. A solar cell (100) comprising:
a) a substrate (110),
b) an absorption layer (120) disposed on the substrate (110), c) a top contact (130) disposed on a portion of a top surface of the absorption layer (120), and
d) a bottom contact (140) is disposed on a portion of a bottom surface of the substrate (110);
wherein the solar cell (100) is characterised in that the absorption layer (120) is laterally divided into at least two absorption regions (121), wherein each absorption region (121) is made of different nanostructured materials having different bandgaps.
2. The solar cell (100) as claimed in claim 1 , wherein the absorption layer (120) is made of either cadmium selenide (CdSe), zinc oxide (ZnO), zinc sulfide (ZnS), cadmium sulphide (CdS), cadmium telluride (CdTe) or lead selenide (PbSe).
3. The solar cell (100) as claimed in claim 1 , wherein the solar cell (100) further includes a coating layer disposed on the absorption layer (120) and the top contact (130).
4. The solar cell (100) as claimed in claim 3, wherein the coating layer includes a splitting wavelength layer.
5. A solar cell (200) comprising:
a) a substrate (210),
b) an absorption layer (220) disposed on the substrate (210), c) a top contact (230) disposed on a portion of a top surface of the absorption layer (220), and
d) a bottom contact (240) is disposed on a portion of a bottom surface of the substrate (210);
wherein the solar cell (200) is characterised in that the absorption layer (220) is laterally divided into at least two absorption regions (221), wherein each absorption region (221) has a particular nano-particle radius size to absorb a particular spectrum of light.
The solar cell (200) as claimed in claim 5, wherein the absorption layer (220) is made of either cadmium selenide (CdSe), zinc oxide (ZnO), zinc sulfide (ZnS), cadmium sulphide (CdS), cadmium telluride (CdTe) or lead selenide (PbSe).
The solar cell (200) as claimed in claim 5, wherein the solar cell (200) further includes a coating layer (250) disposed on the absorption layer (220).
The solar cell (200) as claimed in claim 7, wherein the coating layer (250) includes a splitting wavelength layer.
A method of fabricating a solar cell (200) as claimed in claim 5, comprising the steps of:
a) preparing a substrate (210);
b) spin coating and patterning a photoresist layer (310) on the substrate; c) curing the photoresist layer (310);
d) mixing a nano-particle material having a certain nano-particle radius size with a binder;
e) spin coating the nano-particle mixture (320) on the substrate (210) and the photoresist layer (310);
f) removing the photoresist layer (310) through a lift-off process;
g) functionalizing the binder in the nano-particle mixture (320);
h) repeating steps (b) to (g) until a desired number of absorption regions (221) having varying nano-particle radius size have been deposited on the substrate (210);
i) etching a portion of the top surface of the nano-particle mixtures (320) to remove the binder of the nano-particle mixtures (320); and j) depositing a conductor layer (330) on the etched portion of the nano- particle mixtures (320).
PCT/MY2012/000165 2011-09-09 2012-06-29 A solar cell and method of fabricating thereof WO2013036098A1 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108281552A (en) * 2018-03-06 2018-07-13 电子科技大学 A kind of perovskite solar cell and preparation method thereof with energy band gradient

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4332974A (en) 1979-06-28 1982-06-01 Chevron Research Company Multilayer photovoltaic cell
US6340788B1 (en) 1999-12-02 2002-01-22 Hughes Electronics Corporation Multijunction photovoltaic cells and panels using a silicon or silicon-germanium active substrate cell for space and terrestrial applications
US20080048102A1 (en) * 2006-08-22 2008-02-28 Eastman Kodak Company Optically enhanced multi-spectral detector structure
US20100037935A1 (en) 2008-02-11 2010-02-18 Emcore Solar Power, Inc. Concentrated Photovoltaic System Modules Using III-V Semiconductor Solar Cells
JP2011044511A (en) * 2009-08-20 2011-03-03 Hitachi Zosen Corp Solar cell and method of manufacturing the same, and solar cell device

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4332974A (en) 1979-06-28 1982-06-01 Chevron Research Company Multilayer photovoltaic cell
US6340788B1 (en) 1999-12-02 2002-01-22 Hughes Electronics Corporation Multijunction photovoltaic cells and panels using a silicon or silicon-germanium active substrate cell for space and terrestrial applications
US20080048102A1 (en) * 2006-08-22 2008-02-28 Eastman Kodak Company Optically enhanced multi-spectral detector structure
US20100037935A1 (en) 2008-02-11 2010-02-18 Emcore Solar Power, Inc. Concentrated Photovoltaic System Modules Using III-V Semiconductor Solar Cells
JP2011044511A (en) * 2009-08-20 2011-03-03 Hitachi Zosen Corp Solar cell and method of manufacturing the same, and solar cell device

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
NING C Z ET AL: "Spatially composition-graded alloy semiconductor nanowires and wavelength specific lateral-multijunction full-spectrum solar cells", PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC), 2009 34TH IEEE, IEEE, PISCATAWAY, NJ, USA, 7 June 2009 (2009-06-07), pages 1492 - 1495, XP031626618, ISBN: 978-1-4244-2949-3 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108281552A (en) * 2018-03-06 2018-07-13 电子科技大学 A kind of perovskite solar cell and preparation method thereof with energy band gradient

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