Plasmonic solar cell
Encyclopedia
Plasmonic solar cells are a class of photovoltaic devices that convert light into electricity by using plasmon
s. PSCs are a type of thin-film SC
which are typically 1-2μm thick. They can use substrates which are cheaper than silicon
, such as glass
, plastic
or steel
. The biggest problem for thin film solar cells is that they don’t absorb as much light as the current solar cells. Methods for trapping light on the surface, or in the SC are crucial in order to make thin film SCs viable. One method which has been explored over the past few years is to scatter light using metal nanoparticle
s excited at their surface plasmon resonance
.
This allows light to be absorbed more directly without the relatively thick additional layer required in other types of thin-film solar cells.
can be increased by order of magnitude
when using metal nanoparticles. The increased Raman scattering provides more photon
s to become available to excite surface plasmon
s which cause electron
s to be excited and travel through the thin film SC to create a current. The list below shows a few of research which has been done to improve PSCs.
Current SCs trap light by creating pyramid
s on the surface which have dimensions bigger than most thin film SCs. Making the surface of the substrate rough (typically by growing SnO2 or ZnO on surface) with dimensions on the order of the incoming wavelength
s and depositing the SC on top has been explored. This method increases the photocurrent
, but the thin film SC would then have poor material quality.
The second generation SCs are based on thin film
technologies such as those presented here. These SCs focus on lowering the amount of material used as well as increasing the energy production. Third generation SCs are currently being researched. They focus on reducing the cost of the second generation SCs.
The third generation SCs are discussed in more detail under recent advancement.
is strong enough, electrons can be moved and collected to produce a photocurrent. The thin film of metal in this design must have nanometer sized grooves which act as waveguide
s for the incoming light in order to excite as many photons in the silicon thin film as possible.
This shows the scattering of light for particles which have diameters below the wavelength of light.
This shows the absorption for a point dipole model.
This is the polarizability of the particle. V is the particle volume.
is the dielectric function of the particle. 
is the dielectric function of the embedding medium. When 
the polarizability
of the particle becomes large. This polarizability value is known as the surface plasmon resonance. The dielectric function for metals with low absorption can be defined as:
In the previous equation,
is the bulk plasma frequency. This is defined as:
N is the density of free electrons, e is the electronic charge and m is the effective mass
of an electron.
is the dielectric constant of free space. The equation for the surface plasmon resonance in free space can therefore be represented by:
Many of the plasmonic solar cells use nanoparticles to enhance the scattering of light. These nanoparticles take the shape of spheres, and therefore the surface plasmon resonance frequency for spheres is desirable. By solving the previous equation
s, the surface plasmon resonance frequency for a sphere in free space can be shown as:
As an example, at the surface plasmon resonance for a silver nanoparticle, the scattering cross-section is about 10x the cross-section of the nanoparticle. The goal of the nanoparticles is to trap light on the surface of the SC. The absorption of light is not important for the nanoparticle, rather, it is important for the SC. One would think that if the nanoparticle is increased in size, then the scattering cross-section becomes larger. This is true, however, when compared with the size of the nanoparticle, the ratio (
) is reduced. Particles with a large scattering cross section tend to have a broader plasmon resonance range.
If the dielectric constant for the embedding medium is varied, the resonant frequency can be shifted. Higher indexes of refraction will lead to a longer wavelength frequency.
, such as silicon or silicon nitride
. When performing experiment and simulations on the amount of light scattered into the substrate due to the distance between the particle and substrate, air is used as the embedding material as a reference. It has been found that the amount of light radiated into the substrate decreases with distance from the substrate. This means that nanoparticles on the surface are desirable for radiating light into the substrate, but if there is no distance between the particle and substrate, then the light is not trapped and more light escapes.
The surface plasmons are the excitations of the conduction electrons at the interface of metal and the dielectric. Metallic nanoparticles can be used to couple and trap freely propagating plane waves into the semiconductor thin film layer. Light can be folded into the absorbing layer to increase the absorption. The localized surface plasmons in metal nanoparticles and the surface plasmon polaritons at the interface of metal and semiconductor are of interest in the current research. In recent reported papers, the shape and size of the metal nanoparticles are key factors to determine the incoupling efficiency. The smaller particles have larger incoupling efficiency due to the enhanced near-field coupling. However, very small particles suffer from large ohmic losses.
s on the surface of the film, different frequencies can be obtained. The surface plasmons are also preserved through the use of waveguides as they make the surface plasmons easier to travel on the surface and the losses due to resistance and radiation are minimized. The electric field generated by the surface plasmons influences the electrons to travel toward the collecting substrate.
and gasoline
. The movement toward a more green world has helped to spark research in the area of plasmonic solar cells. Currently, solar cells cannot exceed efficiencies of about 30% (First Generation). With new technologies (Third Generation), efficiencies of up to 40-60% can be expected. With a reduction of materials through the use of thin film technology (Second Generation), prices can be driven lower.
vehicles. A main contribution for this would be the reduced weight of the solar cells. An external fuel source would also not be needed if enough power could be generated from the solar cells. This would drastically help to reduce the weight as well.
. An estimated two million villages near the equator have limited access to electricity and fossil fuels and that approximately 80% of people in the world do not have access to electricity. When the cost of extending power grids, running rural electricity and using diesel generators is compared with the cost of solar cells, many times the solar cells win. If the efficiency and cost of the current solar cell technology is decreased even further, then many rural communities and villages around the world could obtain electricity when current methods are out of the question. Specific applications for rural communities would be water pumping systems, residential electric supply and street lights. A particularly interesting application would be for health systems in countries where motorized vehicles are not overly abundant. Solar cells could be used to provide the power to refrigerate medication
s in coolers during transport.
Solar cells could also provide power to lighthouse
s, buoy
s, or even battleship
s out in the ocean. Industrial companies could use them to power telecommunications systems or monitoring and control systems along pipelines or other system.
s could be built in order to provide power to the electrical grids. With a reduction in size, they could be implemented on both commercial and residential buildings with a much smaller footprint. They might not even seem like an eyesore
.
Other areas are in hybrid systems. The solar cells could help to power high consumption devices such as automobile
s in order to reduce the amount of fossil fuels used and to help improve the environmental conditions of the earth.
s.
has discovered a photonic waveguide which collects light at a certain wavelength and traps it within the structure. This new structure can contain 95% of the light that enters it compared to 30% for other traditional waveguides. It can also direct the light within one wavelength which is ten times greater than traditional waveguides. The wavelength this device captures can be selected by changing the structure of the lattice which comprises the structure. If this structure is used to trap light and keep it in the structure until the solar cell can absorb it, the efficiency of the solar cell could be increased dramatically.
The lattice structure in each of the thin film cells needs to be the same. If it is not then there will be losses. The processes used for depositing the layers are complex. They include Molecular Beam Epitaxy and Metal Organic Vapour Phase Epitaxy. The current efficiency record is made with this process but doesn't have exact matching lattice constants. The losses due to this are not as effective because the differences in lattices allows for more optimal band gap material for the first two cells. This type of cell is expected to be able to be 50% efficient.
Lower quality materials that use cheaper deposition processes are being researched as well. These devices are not as efficient, but the price, size and power combined allow them to be just as cost effective. Since the processes are simpler and the materials are more readily available, the mass production of these devices is more economical.
Plasmon
In physics, a plasmon is a quantum of plasma oscillation. The plasmon is a quasiparticle resulting from the quantization of plasma oscillations just as photons and phonons are quantizations of light and mechanical vibrations, respectively...
s. PSCs are a type of thin-film SC
Thin film solar cell
A thin-film solar cell , also called a thin-film photovoltaic cell , is a solar cell that is made by depositing one or more thin layers of photovoltaic material on a substrate...
which are typically 1-2μm thick. They can use substrates which are cheaper than silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
, such as glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
, plastic
Plastic
A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...
or steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
. The biggest problem for thin film solar cells is that they don’t absorb as much light as the current solar cells. Methods for trapping light on the surface, or in the SC are crucial in order to make thin film SCs viable. One method which has been explored over the past few years is to scatter light using metal nanoparticle
Nanoparticle
In nanotechnology, a particle is defined as a small object that behaves as a whole unit in terms of its transport and properties. Particles are further classified according to size : in terms of diameter, coarse particles cover a range between 10,000 and 2,500 nanometers. Fine particles are sized...
s excited at their surface plasmon resonance
Surface plasmon resonance
The excitation of surface plasmons by light is denoted as a surface plasmon resonance for planar surfaces or localized surface plasmon resonance for nanometer-sized metallic structures....
.
This allows light to be absorbed more directly without the relatively thick additional layer required in other types of thin-film solar cells.
People
There have been quite a few pioneers working with plasmonic solar cells. One of the main focuses has been on improving the thin film SC through the use of metal nanoparticles distributed on the surface. It has been found that the Raman scatteringRaman scattering
Raman scattering or the Raman effect is the inelastic scattering of a photon. It was discovered by Sir Chandrasekhara Venkata Raman and Kariamanickam Srinivasa Krishnan in liquids, and by Grigory Landsberg and Leonid Mandelstam in crystals....
can be increased by order of magnitude
Order of magnitude
An order of magnitude is the class of scale or magnitude of any amount, where each class contains values of a fixed ratio to the class preceding it. In its most common usage, the amount being scaled is 10 and the scale is the exponent being applied to this amount...
when using metal nanoparticles. The increased Raman scattering provides more photon
Photon
In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
s to become available to excite surface plasmon
Surface plasmon
Surface plasmons , are coherent electron oscillations that exist at the interface between any two materials where the real part of the dielectric function changes sign across the interface...
s which cause electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
s to be excited and travel through the thin film SC to create a current. The list below shows a few of research which has been done to improve PSCs.
- Stuart and Hall: Photocurrent enhancement by 18x with 165 nm SOI photodetectorPhotodetectorPhotosensors or photodetectors are sensors of light or other electromagnetic energy. There are several varieties:*Active pixel sensors are image sensors consisting of an integrated circuit that contains an array of pixel sensors, each pixel containing a both a light sensor and an active amplifier...
with wavelength of 800 nm using silver nanoparticles used for scattering and absorption of light.
- Schaadt: Gold nanoparticles used for scattering and absorption of light on doped silicon obtaining 80% enhancements with 500 nm wavelength.
- Derkacs: Gold nanoparticles on thin-film silicon gaining 8% on conversion efficiency.
- Pillai: Silver particles on SOI obtaining 33% photocurrent increase.
- Stenzel: Enhancements in photocurrent by a factor of 2.7 for ITO-copper phthalocyaninePhthalocyaninePhthalocyanine is an intensely blue-green coloured macrocyclic compound that is widely used in dyeing. Phthalocyanines form coordination complexes with most elements of the periodic table...
-indiumIndiumIndium is a chemical element with the symbol In and atomic number 49. This rare, very soft, malleable and easily fusible post-transition metal is chemically similar to gallium and thallium, and shows the intermediate properties between these two...
structures.
- Westphalen: Enhancement for silver clusters incorporated into ITO and zincZincZinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
phthalocyanine solar cells.
- Rand: Enhanced efficiencies for ultra thin film organic solar cells due to 5 nm diameter silver nanoparticles.
Devices
There are currently three different generations of SCs. The first generation (those in the market today) are made with crystalline semiconductor wafers, typically silicon. These are the SCs everybody thinks of when they hear "Solar Cell".Current SCs trap light by creating pyramid
Pyramid
A pyramid is a structure whose outer surfaces are triangular and converge at a single point. The base of a pyramid can be trilateral, quadrilateral, or any polygon shape, meaning that a pyramid has at least three triangular surfaces...
s on the surface which have dimensions bigger than most thin film SCs. Making the surface of the substrate rough (typically by growing SnO2 or ZnO on surface) with dimensions on the order of the incoming wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
s and depositing the SC on top has been explored. This method increases the photocurrent
Photocurrent
Photocurrent is the current that flows through a photosensitive device, such as a photodiode, as the result of exposure to radiant power.The photocurrent may occur as a result of the photoelectric, photoemissive, or photovoltaic effect....
, but the thin film SC would then have poor material quality.
The second generation SCs are based on thin film
Thin film
A thin film is a layer of material ranging from fractions of a nanometer to several micrometers in thickness. Electronic semiconductor devices and optical coatings are the main applications benefiting from thin film construction....
technologies such as those presented here. These SCs focus on lowering the amount of material used as well as increasing the energy production. Third generation SCs are currently being researched. They focus on reducing the cost of the second generation SCs.
The third generation SCs are discussed in more detail under recent advancement.
Design
The design for a PSC varies depending on the method being used to trap and scatter light across the surface and through the material.Metal Nanoparticle Plasmonic Solar Cell
A common design is to deposit metal nanoparticles on the top surface of the thin film SC. When light hits these metal nanoparticles at their surface plasmon resonance, the light is scattered in many different directions. This allows light to travel along the SC and bounce between the substrate and the nanoparticles enabling the SC to absorb more light.Metal Film Plasmonic Solar Cell
Other methods utilizing surface plasmons for harvesting solar energy are available. One other type of structure is to have a thin film of silicon and a thin layer of metal deposited on the lower surface. The light will travel through the silicon and generate surface plasmons on the interface of the silicon and metal. This generates electric fields inside of the silicon since electric fields do not travel very far into metals. If the electric fieldElectric field
In physics, an electric field surrounds electrically charged particles and time-varying magnetic fields. The electric field depicts the force exerted on other electrically charged objects by the electrically charged particle the field is surrounding...
is strong enough, electrons can be moved and collected to produce a photocurrent. The thin film of metal in this design must have nanometer sized grooves which act as waveguide
Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
s for the incoming light in order to excite as many photons in the silicon thin film as possible.
General
When a photon is excited in the substrate of a SC, an electron and hole are separated. Once the electrons and holes are separated, they will want to recombine since they are of opposite charge. If the electrons can be collected prior to this happening then the SC is pretty efficient. The way to collect the electrons quickly would be to make the conducting material very thin. If the surface is made very thin, there will be less light absorbed by the device. A thick device absorbs more light.Scattering and Absorption
The basic principles for the functioning of plasmonic solar cells include scattering and absorption of light due to the deposition of metal nanoparticles. Silicon does not absorb light very well. For this reason, more light needs to be scattered across the surface in order to increase the absorption. It has been found that metal nanoparticles help to scatter the incoming light across the surface of the silicon substrate. The equations that govern the scattering and absorption of light can be shown as:
This shows the scattering of light for particles which have diameters below the wavelength of light.
This shows the absorption for a point dipole model.
This is the polarizability of the particle. V is the particle volume.
is the dielectric function of the particle. is the dielectric function of the embedding medium. When the polarizabilityPolarizability
Polarizability is the measure of the change in a molecule's electron distribution in response to an applied electric field, which can also be induced by electric interactions with solvents or ionic reagents. It is a property of matter...
of the particle becomes large. This polarizability value is known as the surface plasmon resonance. The dielectric function for metals with low absorption can be defined as:
In the previous equation,
is the bulk plasma frequency. This is defined as:
N is the density of free electrons, e is the electronic charge and m is the effective mass
Effective mass
In solid state physics, a particle's effective mass is the mass it seems to carry in the semiclassical model of transport in a crystal. It can be shown that electrons and holes in a crystal respond to electric and magnetic fields almost as if they were particles with a mass dependence in their...
of an electron.
is the dielectric constant of free space. The equation for the surface plasmon resonance in free space can therefore be represented by:
Many of the plasmonic solar cells use nanoparticles to enhance the scattering of light. These nanoparticles take the shape of spheres, and therefore the surface plasmon resonance frequency for spheres is desirable. By solving the previous equation
Equation
An equation is a mathematical statement that asserts the equality of two expressions. In modern notation, this is written by placing the expressions on either side of an equals sign , for examplex + 3 = 5\,asserts that x+3 is equal to 5...
s, the surface plasmon resonance frequency for a sphere in free space can be shown as:
As an example, at the surface plasmon resonance for a silver nanoparticle, the scattering cross-section is about 10x the cross-section of the nanoparticle. The goal of the nanoparticles is to trap light on the surface of the SC. The absorption of light is not important for the nanoparticle, rather, it is important for the SC. One would think that if the nanoparticle is increased in size, then the scattering cross-section becomes larger. This is true, however, when compared with the size of the nanoparticle, the ratio (
) is reduced. Particles with a large scattering cross section tend to have a broader plasmon resonance range.Wavelength Dependence
Surface plasmon resonance mainly depends on the density of free electrons in the particle. The order of densities of electrons for different metals is shown below along with the type of light which corresponds to the resonance.- Aluminum - Ultra-violet
- SilverSilverSilver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...
- Ultra-violet - GoldGoldGold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
- Visible - CopperCopperCopper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
- Visible
If the dielectric constant for the embedding medium is varied, the resonant frequency can be shifted. Higher indexes of refraction will lead to a longer wavelength frequency.
Light Trapping
The metal nanoparticles are deposited at a distance from the substrate in order to trap the light between the substrate and the particles. The particles are embedded in a material on top of the substrate. The material is typically a dielectricDielectric
A dielectric is an electrical insulator that can be polarized by an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material, as in a conductor, but only slightly shift from their average equilibrium positions causing dielectric...
, such as silicon or silicon nitride
Silicon nitride
Silicon nitride is a chemical compound of silicon and nitrogen. If powdered silicon is heated between 1300° and 1400°C in an atmosphere of nitrogen, trisilicon tetranitride, Si3N4, is formed. The silicon sample weight increases progressively due to the chemical combination of silicon and nitrogen...
. When performing experiment and simulations on the amount of light scattered into the substrate due to the distance between the particle and substrate, air is used as the embedding material as a reference. It has been found that the amount of light radiated into the substrate decreases with distance from the substrate. This means that nanoparticles on the surface are desirable for radiating light into the substrate, but if there is no distance between the particle and substrate, then the light is not trapped and more light escapes.
The surface plasmons are the excitations of the conduction electrons at the interface of metal and the dielectric. Metallic nanoparticles can be used to couple and trap freely propagating plane waves into the semiconductor thin film layer. Light can be folded into the absorbing layer to increase the absorption. The localized surface plasmons in metal nanoparticles and the surface plasmon polaritons at the interface of metal and semiconductor are of interest in the current research. In recent reported papers, the shape and size of the metal nanoparticles are key factors to determine the incoupling efficiency. The smaller particles have larger incoupling efficiency due to the enhanced near-field coupling. However, very small particles suffer from large ohmic losses.
Metal Film
As light is incident upon the surface of the metal film, it excites surface plasmons. The surface plasmon frequency is specific for the material, but through the use of gratingGrating
A grating is any regularly spaced collection of essentially identical, parallel, elongated elements. Gratings usually consist of a single set of elongated elements, but can consist of two sets, in which case the second set is usually perpendicular to the first...
s on the surface of the film, different frequencies can be obtained. The surface plasmons are also preserved through the use of waveguides as they make the surface plasmons easier to travel on the surface and the losses due to resistance and radiation are minimized. The electric field generated by the surface plasmons influences the electrons to travel toward the collecting substrate.
Materials
| First Generation | Second Generation | Third Generation |
|---|---|---|
| Single-crystal silicon | CuInSe2 | Gallium Indium Phosphide |
| Multicrystalline silicon | amorphous silicon | Gallium Indium Arsenide |
| Polycrystalline silicon | thin film crystalline Si | Germanium |
Applications
The applications for plasmonic solar cells are endless. The need for cheaper and more efficient solar cells is huge. In order for solar cells to be considered cost effective, they need to provide energy for a smaller price than that of traditional power sources such as coalCoal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
and gasoline
Gasoline
Gasoline , or petrol , is a toxic, translucent, petroleum-derived liquid that is primarily used as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain...
. The movement toward a more green world has helped to spark research in the area of plasmonic solar cells. Currently, solar cells cannot exceed efficiencies of about 30% (First Generation). With new technologies (Third Generation), efficiencies of up to 40-60% can be expected. With a reduction of materials through the use of thin film technology (Second Generation), prices can be driven lower.
Space
Certain applications for plasmonic solar cells would be for space explorationSpace exploration
Space exploration is the use of space technology to explore outer space. Physical exploration of space is conducted both by human spaceflights and by robotic spacecraft....
vehicles. A main contribution for this would be the reduced weight of the solar cells. An external fuel source would also not be needed if enough power could be generated from the solar cells. This would drastically help to reduce the weight as well.
Rural
Solar cells have a great potential to help rural electrificationElectrification
Electrification originally referred to the build out of the electrical generating and distribution systems which occurred in the United States, England and other countries from the mid 1880's until around 1940 and is in progress in developing countries. This also included the change over from line...
. An estimated two million villages near the equator have limited access to electricity and fossil fuels and that approximately 80% of people in the world do not have access to electricity. When the cost of extending power grids, running rural electricity and using diesel generators is compared with the cost of solar cells, many times the solar cells win. If the efficiency and cost of the current solar cell technology is decreased even further, then many rural communities and villages around the world could obtain electricity when current methods are out of the question. Specific applications for rural communities would be water pumping systems, residential electric supply and street lights. A particularly interesting application would be for health systems in countries where motorized vehicles are not overly abundant. Solar cells could be used to provide the power to refrigerate medication
Medication
A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...
s in coolers during transport.
Solar cells could also provide power to lighthouse
Lighthouse
A lighthouse is a tower, building, or other type of structure designed to emit light from a system of lamps and lenses or, in older times, from a fire, and used as an aid to navigation for maritime pilots at sea or on inland waterways....
s, buoy
Buoy
A buoy is a floating device that can have many different purposes. It can be anchored or allowed to drift. The word, of Old French or Middle Dutch origin, is now most commonly in UK English, although some orthoepists have traditionally prescribed the pronunciation...
s, or even battleship
Battleship
A battleship is a large armored warship with a main battery consisting of heavy caliber guns. Battleships were larger, better armed and armored than cruisers and destroyers. As the largest armed ships in a fleet, battleships were used to attain command of the sea and represented the apex of a...
s out in the ocean. Industrial companies could use them to power telecommunications systems or monitoring and control systems along pipelines or other system.
High Power
If the solar cells could be produced on a large scale and be cost effective then entire power stationPower station
A power station is an industrial facility for the generation of electric energy....
s could be built in order to provide power to the electrical grids. With a reduction in size, they could be implemented on both commercial and residential buildings with a much smaller footprint. They might not even seem like an eyesore
Eyesore
An eyesore is an unpleasant view. Its technical usage is as an alternative perspective to the notion of landmark. Common examples include dilapidated buildings, graffiti, litter, polluted areas and excessive commercial signage such as billboards. Some eyesores may be a matter of opinion such as...
.
Other areas are in hybrid systems. The solar cells could help to power high consumption devices such as automobile
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
s in order to reduce the amount of fossil fuels used and to help improve the environmental conditions of the earth.
Low Power
One application which has not been mentioned is consumer electronics. Essentially, solar cells could be used to replace batteries for low power electronics. This would save everyone a lot of money and it would also help to reduce the amount of waste going into landfillLandfill
A landfill site , is a site for the disposal of waste materials by burial and is the oldest form of waste treatment...
s.
Light Trapping
As discussed earlier, being able to concentrate and scatter light across the surface of the plasmonic solar cell will help to increase efficiencies. Recently, research at Sandia National LaboratoriesSandia National Laboratories
The Sandia National Laboratories, managed and operated by the Sandia Corporation , are two major United States Department of Energy research and development national laboratories....
has discovered a photonic waveguide which collects light at a certain wavelength and traps it within the structure. This new structure can contain 95% of the light that enters it compared to 30% for other traditional waveguides. It can also direct the light within one wavelength which is ten times greater than traditional waveguides. The wavelength this device captures can be selected by changing the structure of the lattice which comprises the structure. If this structure is used to trap light and keep it in the structure until the solar cell can absorb it, the efficiency of the solar cell could be increased dramatically.
Absorption
Another recent advancement in plasmonic solar cells is using other methods to aid in the absorption of light. One way being researched is the use of metal wires on top of the substrate to scatter the light. This would help by utilizing a larger area of the surface of the solar cell for light scattering and absorption. The danger in using lines instead of dots would be creating a reflective layer which would reject light from the system. This is very undesirable for solar cells. This would be very similar to the thin metal film approach, but it also utilizes the scattering effect of the nanoparticles.Third Generation Solar Cells
The goal of third generation solar cells is to increase the efficiency using second generation solar cells (thin film) and using materials that are found abundantly on earth. This has also been a goal of the thin film solar cells. With the use of common and safe materials, third generation solar cells should be able to be manufactured in mass quantities further reducing the costs. The initial costs would be high in order to produce the manufacturing processes, but after that they should be cheap. The way third generation solar cells will be able to improve efficiency is to absorb a wider range of frequencies. The current thin film technology has been limited to one frequency due to the use of single band gap devices.Multiple Energy Levels
The idea for multiple energy level solar cells is to basically stack thin film solar cells on top of each other. Each thin film solar cell would have a different band gap which means that if part of the solar spectrum was not absorbed by the first cell then the one just below would be able to absorb part of the spectrum. These can be stacked and an optimal band gap can be used for each cell in order to produce the maximum amount of power. Options for how each cell is connected are available, such as serial or parallel. The serial connection is desired because the output of the solar cell would just be two leads.The lattice structure in each of the thin film cells needs to be the same. If it is not then there will be losses. The processes used for depositing the layers are complex. They include Molecular Beam Epitaxy and Metal Organic Vapour Phase Epitaxy. The current efficiency record is made with this process but doesn't have exact matching lattice constants. The losses due to this are not as effective because the differences in lattices allows for more optimal band gap material for the first two cells. This type of cell is expected to be able to be 50% efficient.
Lower quality materials that use cheaper deposition processes are being researched as well. These devices are not as efficient, but the price, size and power combined allow them to be just as cost effective. Since the processes are simpler and the materials are more readily available, the mass production of these devices is more economical.