16-07-2013, 04:02 PM
NANO SCIENCE IN SOLAR ENERGY
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INTRODUCTION
The growing energy demand and the depletion of conventional energy sources along with global warming threats has motivated researchers to design the most efficient photovoltaic (PV) cells. A PV cell that used sunlight to generate clean electric power was first designed and fabricated by Bell Laboratories in 1955 . Over the last five decades, numerous studies have reported the notable progress in PV cells design and performance for terrestrial applications . Several pioneering research and development have been conducted on crystalline silicon cells, amorphous silicon cells, CIGS (copper-in diumgallium- diselenide) solar cells and other compound solar cells, and dye-sensitized solar cells. Crystalline silicon cells, having a conversion efficiency of over 20 % over a small area, dominate the
recent trend of PV cell market. However, a solar cell module with crystalline silicon is expensive. In order to reduce the production cost, research is being performed to develop thin-film solar cells with a thickness of under 100 _ m at low temperature. On the other hand, amorphous silicon cells with a thickness of a few micrometers are inexpensive and can be used for mass production. But their efficiency is relatively low. Further investigation is continuing for developing microcrystalline silicon cells with laminated structures to improve cell efficiency. Whereas, CIGS solar cells have a potential to obtain cell efficiencies near 20 % over a small cell area, the efficiency drops sharply over a large area. Dye-sensitized solar cells are relatively inexpensive.
In the last few years, extensive research has been conducted to reach cell efficiencies over 10 % over a small cell area.
This paper reviews the remarkable performance of traditional PV cells and outlines the possible areas for further investigation. Use of nanotechnology in hybrid solar cell design could further improve the performance and reduce the cost of PV cells and modules. Basic principles, mechanisms and challenges within three key areas of nano technology have been discussed from a clean energy perspective.
THREE GENERATIONS OF SOLAR PANELS
Photovoltaic technology has been categorized into three distinct generations, which mark step shifts in the materials and manufacturing techniques used to make the cells.
The first generation of solar cells uses very high quality crystalline silicon. These are expensive to manufacture, and have a fairly low theoretical efficiency limit of around 33%. Second generation PV cells use thin film technologies with other semiconducting materials such as cadmium telluride (CdTe) and copper indium gallium selenide (CIGS). These materials can significantly reduce processing costs, and promise much higher theoretical efficiencies than silicon-based PV materials. Third generation PV is a much broader group of technologies, all of which are emerging or in the development phases. Technologies often considered part of this third generation include quantum dots, nanostructured semiconductors, and amorphous silicon.
TRADITIONAL PV CELLS
Extensive research has been performed with crystalline, nanocrystalline, multicrystalline, thin-film polycrystalline, and amorphous solar cells to maximize cell efficiency as well as to reduce material size and cost. The concept of crystalline silicon thin-film solar cells of thickness fewer than 50nm reduces silicon material consumption significantly and has potential to reach high efficiencies comparable to silicon wafer. The reducing thickness of a solar cell results in an increase open-circuit voltage. However, the crystalline silicon technology has had the growing demand depending upon cell
performance and costs compared to the other forms . On the other hand, solar cell efficiency has also been improved by developing multi junction devices as tuned to collect light at a certain wavelength, which converts varying wavelengths of sunlight into electricity. Stacks of exotic semiconductor materials composed of gallium, indium, phosphorous, germanium, and arsenic have been
used to develop multilayered systems. However, the costs of these semiconductor materials increase solar cell module cost significantly than that of silicon.
SCIENCE OF SILICON PV CELLS
Scientific base for solar PV electric power generation is solid-state physics
of semiconductors. Silicon is a popular candidate material for solar PV cells because
It is a semiconductor material.
Technology is well developed to make silicon to be positive (+ve)
or negative (-ve) charge-carriers – essential elements for an
electric cell or battery
Silicon is abundant in supply and relatively inexpensive in production
Micro- and nano-technologies have enhanced the opto-electricity
conversion efficiency of silicon solar PV cells
Thin-Film Solar Cells
Thin film CIGS technology is very promising for achieving high efficiency at economic price. An ink based non-vacuum process is used to fabricate CIGS solar cells both on rigid and flexible substrates. An aqueous precursor metal-oxide suspension made from nanoparticles of Cu, Ia, and Ga oxides is coated onto a Mo foil or a non-conducting substrate, improving cell efficiency to 8.9 % on polyimide, 13.0 % on Mo foil, and
13.6 % on glass substrate . The recorded efficiency of ZnO / CdS / CuInGaSe2 thinfilm solar cells with preferred orientation and absorber materials is 19.2% dueto higher open-circuit photovoltage (Voc) and short-circuit photocurrent density (Jsc) . The performance of a thin film single junction GaAs solar cell is improved with a gold mirror back contact, which reflects 90% of the high wavelength photons and serves as low ohmic back contact and also reduces the thickness to half that of the regular
GaAs cell film thickness with reported cell efficiency of 24.5% AM1.5G .
NANO-MATERIALS
There is an active research and development of nano-technology, nano-material, which are of size of a 10-9 meter, offer different chemical and physical properties from the same materials in their normal form. They can be adaptive to new technologies and have the potential use in making more efficient solar cells and catalysts that can be used in hydrogen-powered fuel cells.
Due to small size and excellent conductivity, CNT’S (carbon nano-tubes), can possibly be used as base resource of future electronic devices. CNT cables could be used to make electricity transmission lines, which will give us, large performance improvement over present day power lines.
INTRODUCTOIN TO SOLAR-ENERGY
Solar energy is an enigma of its own. Based on the current costs of producing solar panels and the rate at which these costs have been dropping, it is evident that solar power would become a major source of power in projection of future energy sources. If the current projections based on the NREL model are correct, solar power could soon be a very competitive source of energy while addressing the problem of producing power without generating carbon dioxide and other effluents. It would not be subject to any kind of risk. It is impossible to embargo the sun. The budget for solar research is around seventy million dollars in the west, and most forecast of source of energy in future give solar a minor role.
CONCLUSION
The conclusion obtained from the above topic is that we should increase the use of renewable sources of energy and decrease the use of non-renewable resources. Existing renewable resources are well established. It has been seen through the various articles that available renewable energy resources are helping in the production of the other forms of energy, which makes our energy system more strong and economical. Likewise the production of solar energy, from the available sunlight, and its usage is more clean, safe and efficient. They are commercially available and are being utilized. The new upcoming technologies in renewable resources are very promising but a lot more research and infrastructure is required before it can be adapted.
[attachment=56635]
INTRODUCTION
The growing energy demand and the depletion of conventional energy sources along with global warming threats has motivated researchers to design the most efficient photovoltaic (PV) cells. A PV cell that used sunlight to generate clean electric power was first designed and fabricated by Bell Laboratories in 1955 . Over the last five decades, numerous studies have reported the notable progress in PV cells design and performance for terrestrial applications . Several pioneering research and development have been conducted on crystalline silicon cells, amorphous silicon cells, CIGS (copper-in diumgallium- diselenide) solar cells and other compound solar cells, and dye-sensitized solar cells. Crystalline silicon cells, having a conversion efficiency of over 20 % over a small area, dominate the
recent trend of PV cell market. However, a solar cell module with crystalline silicon is expensive. In order to reduce the production cost, research is being performed to develop thin-film solar cells with a thickness of under 100 _ m at low temperature. On the other hand, amorphous silicon cells with a thickness of a few micrometers are inexpensive and can be used for mass production. But their efficiency is relatively low. Further investigation is continuing for developing microcrystalline silicon cells with laminated structures to improve cell efficiency. Whereas, CIGS solar cells have a potential to obtain cell efficiencies near 20 % over a small cell area, the efficiency drops sharply over a large area. Dye-sensitized solar cells are relatively inexpensive.
In the last few years, extensive research has been conducted to reach cell efficiencies over 10 % over a small cell area.
This paper reviews the remarkable performance of traditional PV cells and outlines the possible areas for further investigation. Use of nanotechnology in hybrid solar cell design could further improve the performance and reduce the cost of PV cells and modules. Basic principles, mechanisms and challenges within three key areas of nano technology have been discussed from a clean energy perspective.
THREE GENERATIONS OF SOLAR PANELS
Photovoltaic technology has been categorized into three distinct generations, which mark step shifts in the materials and manufacturing techniques used to make the cells.
The first generation of solar cells uses very high quality crystalline silicon. These are expensive to manufacture, and have a fairly low theoretical efficiency limit of around 33%. Second generation PV cells use thin film technologies with other semiconducting materials such as cadmium telluride (CdTe) and copper indium gallium selenide (CIGS). These materials can significantly reduce processing costs, and promise much higher theoretical efficiencies than silicon-based PV materials. Third generation PV is a much broader group of technologies, all of which are emerging or in the development phases. Technologies often considered part of this third generation include quantum dots, nanostructured semiconductors, and amorphous silicon.
TRADITIONAL PV CELLS
Extensive research has been performed with crystalline, nanocrystalline, multicrystalline, thin-film polycrystalline, and amorphous solar cells to maximize cell efficiency as well as to reduce material size and cost. The concept of crystalline silicon thin-film solar cells of thickness fewer than 50nm reduces silicon material consumption significantly and has potential to reach high efficiencies comparable to silicon wafer. The reducing thickness of a solar cell results in an increase open-circuit voltage. However, the crystalline silicon technology has had the growing demand depending upon cell
performance and costs compared to the other forms . On the other hand, solar cell efficiency has also been improved by developing multi junction devices as tuned to collect light at a certain wavelength, which converts varying wavelengths of sunlight into electricity. Stacks of exotic semiconductor materials composed of gallium, indium, phosphorous, germanium, and arsenic have been
used to develop multilayered systems. However, the costs of these semiconductor materials increase solar cell module cost significantly than that of silicon.
SCIENCE OF SILICON PV CELLS
Scientific base for solar PV electric power generation is solid-state physics
of semiconductors. Silicon is a popular candidate material for solar PV cells because
It is a semiconductor material.
Technology is well developed to make silicon to be positive (+ve)
or negative (-ve) charge-carriers – essential elements for an
electric cell or battery
Silicon is abundant in supply and relatively inexpensive in production
Micro- and nano-technologies have enhanced the opto-electricity
conversion efficiency of silicon solar PV cells
Thin-Film Solar Cells
Thin film CIGS technology is very promising for achieving high efficiency at economic price. An ink based non-vacuum process is used to fabricate CIGS solar cells both on rigid and flexible substrates. An aqueous precursor metal-oxide suspension made from nanoparticles of Cu, Ia, and Ga oxides is coated onto a Mo foil or a non-conducting substrate, improving cell efficiency to 8.9 % on polyimide, 13.0 % on Mo foil, and
13.6 % on glass substrate . The recorded efficiency of ZnO / CdS / CuInGaSe2 thinfilm solar cells with preferred orientation and absorber materials is 19.2% dueto higher open-circuit photovoltage (Voc) and short-circuit photocurrent density (Jsc) . The performance of a thin film single junction GaAs solar cell is improved with a gold mirror back contact, which reflects 90% of the high wavelength photons and serves as low ohmic back contact and also reduces the thickness to half that of the regular
GaAs cell film thickness with reported cell efficiency of 24.5% AM1.5G .
NANO-MATERIALS
There is an active research and development of nano-technology, nano-material, which are of size of a 10-9 meter, offer different chemical and physical properties from the same materials in their normal form. They can be adaptive to new technologies and have the potential use in making more efficient solar cells and catalysts that can be used in hydrogen-powered fuel cells.
Due to small size and excellent conductivity, CNT’S (carbon nano-tubes), can possibly be used as base resource of future electronic devices. CNT cables could be used to make electricity transmission lines, which will give us, large performance improvement over present day power lines.
INTRODUCTOIN TO SOLAR-ENERGY
Solar energy is an enigma of its own. Based on the current costs of producing solar panels and the rate at which these costs have been dropping, it is evident that solar power would become a major source of power in projection of future energy sources. If the current projections based on the NREL model are correct, solar power could soon be a very competitive source of energy while addressing the problem of producing power without generating carbon dioxide and other effluents. It would not be subject to any kind of risk. It is impossible to embargo the sun. The budget for solar research is around seventy million dollars in the west, and most forecast of source of energy in future give solar a minor role.
CONCLUSION
The conclusion obtained from the above topic is that we should increase the use of renewable sources of energy and decrease the use of non-renewable resources. Existing renewable resources are well established. It has been seen through the various articles that available renewable energy resources are helping in the production of the other forms of energy, which makes our energy system more strong and economical. Likewise the production of solar energy, from the available sunlight, and its usage is more clean, safe and efficient. They are commercially available and are being utilized. The new upcoming technologies in renewable resources are very promising but a lot more research and infrastructure is required before it can be adapted.