Organic solar cell
Encyclopedia
An organic
photovoltaic cell
(OPVC) is a photovoltaic cell that uses organic electronics
--a branch of electronics that deals with conductive organic polymers or small organic molecules for light absorption and charge transport.
The plastic itself has low production costs in high volumes. Combined with the flexibility of organic molecules, this makes it potentially lucrative for photovoltaic applications. Molecular engineering (e.g. changing the length and functional group
of polymer
s) can change the energy gap, which allows chemical change in these materials. The optical absorption coefficient of organic molecules is high, so a large amount of light can be absorbed with a small amount of materials. The main disadvantages associated with organic photovoltaic cells are low efficiency
, low stability and low strength compared to inorganic photovoltaic cells.
A photovoltaic cell is a specialized semiconductor diode that converts visible light into direct current (DC) electricity. Some photovoltaic cells can also convert infrared (IR) or ultraviolet (UV) radiation into DC. A common characteristic of both the small molecules and polymers (Fig 1) used in photovoltaics
is that they all have large conjugated system
s. A conjugated system is formed where carbon
atoms covalently bond with alternating single and double bonds, in other words these are chemical reactions of hydrocarbons. These hydrocarbons electrons pz orbitals delocalize
and form a delocalized bonding π orbital with a π* antibonding
orbital. The delocalized π orbital is the highest occupied molecular orbital (HOMO
), and the π* orbital is the lowest unoccupied molecular orbital (LUMO
). The separation between HOMO and LUMO is considered as the band gap of organic electronic materials. The band gap is typically in the range of 1-4 eV.
When these materials absorb a photon
, an excited state
is created and confined to a molecule or a region of a polymer chain. The excited state can be regarded as an electron hole pair bound together by electrostatic interactions, i.e. exciton
s. In photovoltaic cells, excitons are broken up into free electrons-hole pairs by effective fields. The effective field are set up by creating a heterojunction between two dissimilar materials. Effective fields break up excitons by causing the electron to fall from the conduction band of the absorber to the conduction band of the acceptor molecule. It is necessary that the acceptor material has a conduction band edge that is lower than that of the absorber material.
Single layer organic photovoltaic cells are the simplest form among various organic photovoltaic cells. These cells are made by sandwiching a layer of organic electronic materials between two metallic conductors, typically a layer of indium tin oxide
(ITO) with high work function and a layer of low work function metal such as Al, Mg and Ca. The basic structure of such a cell is illustrated in Fig 2.
The difference of work function
between the two conductors sets up an electric field in the organic layer. When the organic layer absorbs light, electrons will be excited to Lowest Unoccupied Molecular Orbital
(LUMO) and leave holes in the Highest Occupied Molecular Orbital (HOMO) forming exciton
s. The potential created by the different work functions helps to separate the exciton pairs, pulling electrons to the positive electrode
(an electrical conductor used to make contact with a nonmetallic part of a circuit) and holes to the negative electrode. The current and voltage resulting from this process can be used to do work. Using electric fields is not the best way to break up excitons, heterojunction based cells which rely on effective fields are more effective.
or the creation of voltage of a cell based on magnesium phthalocyanine
a macrocyclic compound having an alternating nitrogen atom-carbon atom ring structure (MgPh), which had a photovoltage of 200mV. Ghosh et al. investigated the Al/MgPh/Ag cell, and obtained photovoltaic efficiency of 0.01% under illumination at 690 nm.
Conjugated polymers were also used in this type of photovoltaic cell. Weinberger et al. used polyacetylene (Fig 1) as the organic layer, Al and graphite as electrodes to fabricate a cell, which had an open circuit voltage of 0.3 V and a charge collection efficiency of 0.3%. Glenis et al. reported a Al/poly(3-nethyl-thiophene)/Pt cell had an external quantum yield of 0.17%, an open circuit voltage of 0.4V and a fill factor of 0.3. Karg et al. fabricated an ITO/PPV/Al cell, showing an open circuit voltage of 1V and a power conversion efficiency of 0.1% under white-light illumination.
This type of organic photovoltaic cell contains two different layers in between the conductive electrodes (Fig 3). These two layers of materials have differences in electron affinity
and ionization energy
, therefore electrostatic forces are generated at the interface between the two layers. The materials are chosen properly to make the differences large enough, so these local electric fields are strong, which may break up the excitons much more efficiently than the single layer photovoltaic cells do. The layer with higher electron affinity and ionization potential is the electron acceptor, and the other layer is the electron donor. This structure is also called planar donor-acceptor heterojunctions.
Perylene derivatives are a group of organic molecules with high electron affinity and chemical stability. Ching W. Tang
deposited a layer of copper phthalcocyanine as electron donor and perylene tetracarboxylic derivative as electron acceptor, fabricating a cell with a fill factor as high as 0.65 and a power conversion efficiency of 1% under simulated AM2 illumination. Halls et al. fabricated a cell with a layer of bis(phenethylimido) perylene over a layer of PPV as the electron donor. This cell had peak external quantum efficiency of 6% and power conversion efficiency of 1% under monochromatic illumination, and the fill factor is up to 0.6.
In this type of photovoltaic cell, the electron donor and acceptor are mixed together, forming a polymer blend (Fig 4). If the length scale of the blend is similar with the exciton diffusion length, most of the excitons generated in either material may reach the interface, where excitons break efficiently. Electrons move to the acceptor domains then were carried through the device and collected by one electrode, and holes were pulled in the opposite direction and collected at the other side.
Polymer/polymer blends are also used in dispersed heterojunction photovoltaic cells. Halls et al. used a blend of CN-PPV and MEH-PPV, fabricated a cell with Al and ITO as the electrodes, whose peak monochromatic power conversion efficiency is 1% and fill factor is 0.38.
Dye sensitized photovoltaic cells can also be considered as important ones of this type.
Other important factors include the exciton diffusion length; charge separation and charge collection; and charge transport and mobility, which are affected by the presence of impurities.
-_highly_folded_hetero-junction,_(b)-_hetero-junction_with_controlled_growth.jpg)
As described in section 2.3, dispersed heterojunction
of donor-acceptor organic materials have high quantum efficiency compared to the planar hetero-junction, because it is more likely for an exciton to find an interface within its diffusion length. Film morphology can also have a drastic effect on the quantum efficiency of the device. Rough surfaces and presence of voids can increase the series resistance and also the chance of short circuiting. Film morphology and as a result quantum efficiency can be improved by annealing of a device after covering it by ~1000Å thick metal cathode. Metal film on top of the organic film applies stresses on the organic film, which helps to prevent the morphological relaxation in the organic film. This gives more densely packed films while at the same time allows the formation of phase-separated interpenetrating donor-acceptor interface inside the bulk of organic thin film.
and vapor-phase deposition. However each method has certain draw backs, spin coating technique can coat larger surface areas with high speed but the use of solvent for one layer can degrade the already existing polymer layer. Another problem is related with the patterning of the substrate for device as spin-coating results in coating the entire substrate with a single material.
_vapor_thermal_evaporation_.jpg)
Another deposition technique is "Vacuum thermal evaporation" (VTE) which involves the heating of an organic material in vacuum. The substrate is placed several centimeters away from the source so that evaporated material may be directly deposited onto the substrate, as shown in Fig 6(a). This method is useful for depositing many layers of different materials without chemical interaction between different layers. However, there are sometimes problems with film-thickness uniformity and uniform doping over large-area substrates. In addition, the materials that deposit on the wall of the chamber can contaminate later depositions. This is "line of sight" technique also can create holes in the film due to shadowing, which causes an increase in the device series-resistance and short circuit.
Another advantage over VTE is the uniformity in evaporation rate. This occurs because the carrier gas becomes saturated with the vapors of the organic material coming out of the source and then moves towards the cooled substrate, Fig6(b). Depending on the growth parameters (temperature of the source, base pressure and flux of the carrier gas) the deposited film can be crystalline or amorphous in nature. Devices fabricated using OVPD show a higher short-circuit current density than that of devices made using VTE. An extra layer of donor-acceptor hetero-junction at the top of the cell may block excitons, whilst allowing conduction of electron; resulting in improved cell efficiency.
Plexcore PV 2000 organic solar ink is able to deliver higher performance in fluorescent lighting conditions in comparison to amorphous silicon
solar cells, and said to have a 30% to 40% increase in indoor power density in comparison to the standard organic solar technology.
Plextronics has also developed a manufacturing method that allows for low-temperature processing of OPV. While previous industry standard techniques required a glass substrate to be annealed
at temperatures at or above 110° C, this method enables annealing at less than 65° C. It is expected to reduce manufacturing costs as it may enable the use of less expensive substrates, especially once the process is transferred to flexible substrates such as plastic
.
Organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, composition, reactions, and preparation of carbon-based compounds, hydrocarbons, and their derivatives...
photovoltaic cell
Solar cell
A solar cell is a solid state electrical device that converts the energy of light directly into electricity by the photovoltaic effect....
(OPVC) is a photovoltaic cell that uses organic electronics
Organic electronics
Organic electronics, plastic electronics or polymer electronics, is a branch of electronics dealing with conductive polymers, plastics, or small molecules. It is called 'organic' electronics because the polymers and small molecules are carbon-based...
--a branch of electronics that deals with conductive organic polymers or small organic molecules for light absorption and charge transport.
The plastic itself has low production costs in high volumes. Combined with the flexibility of organic molecules, this makes it potentially lucrative for photovoltaic applications. Molecular engineering (e.g. changing the length and functional group
Functional group
In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of...
of polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
s) can change the energy gap, which allows chemical change in these materials. The optical absorption coefficient of organic molecules is high, so a large amount of light can be absorbed with a small amount of materials. The main disadvantages associated with organic photovoltaic cells are low efficiency
Energy conversion efficiency
Energy conversion efficiency is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The useful output may be electric power, mechanical work, or heat.-Overview:...
, low stability and low strength compared to inorganic photovoltaic cells.
Organic photovoltaic materials
Photovoltaics
Photovoltaics is a method of generating electrical power by converting solar radiation into direct current electricity using semiconductors that exhibit the photovoltaic effect. Photovoltaic power generation employs solar panels composed of a number of solar cells containing a photovoltaic material...
is that they all have large conjugated system
Conjugated system
In chemistry, a conjugated system is a system of connected p-orbitals with delocalized electrons in compounds with alternating single and multiple bonds, which in general may lower the overall energy of the molecule and increase stability. Lone pairs, radicals or carbenium ions may be part of the...
s. A conjugated system is formed where carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
atoms covalently bond with alternating single and double bonds, in other words these are chemical reactions of hydrocarbons. These hydrocarbons electrons pz orbitals delocalize
Delocalized electron
In chemistry, delocalized electrons are electrons in a molecule, ion or solid metal that are not associated with a single atom or one covalent bond....
and form a delocalized bonding π orbital with a π* antibonding
Antibonding
Antibonding is a type of chemical bonding. An antibonding orbital is a form of molecular orbital that is located outside the region of two distinct nuclei...
orbital. The delocalized π orbital is the highest occupied molecular orbital (HOMO
Homo
Homo may refer to:*the Greek prefix ὅμο-, meaning "the same"*the Latin for man, human being*Homo, the taxonomical genus including modern humans...
), and the π* orbital is the lowest unoccupied molecular orbital (LUMO
Lumo
Lumo is a 2007 documentary film about twenty-year-old Lumo Sinai, a woman who fell victim to "Africa's First World War." While returning home one day, Lumo and another woman were gang-raped by a group of soldiers fighting for control of the Democratic Republic of the Congo during the 1994 Rwandan...
). The separation between HOMO and LUMO is considered as the band gap of organic electronic materials. The band gap is typically in the range of 1-4 eV.
When these materials absorb a 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...
, an excited state
Excited state
Excitation is an elevation in energy level above an arbitrary baseline energy state. In physics there is a specific technical definition for energy level which is often associated with an atom being excited to an excited state....
is created and confined to a molecule or a region of a polymer chain. The excited state can be regarded as an electron hole pair bound together by electrostatic interactions, i.e. exciton
Exciton
An exciton is a bound state of an electron and hole which are attracted to each other by the electrostatic Coulomb force. It is an electrically neutral quasiparticle that exists in insulators, semiconductors and some liquids...
s. In photovoltaic cells, excitons are broken up into free electrons-hole pairs by effective fields. The effective field are set up by creating a heterojunction between two dissimilar materials. Effective fields break up excitons by causing the electron to fall from the conduction band of the absorber to the conduction band of the acceptor molecule. It is necessary that the acceptor material has a conduction band edge that is lower than that of the absorber material.
Single layer organic photovoltaic cell
Indium tin oxide
Indium tin oxide is a solid solution of indium oxide and tin oxide , typically 90% In2O3, 10% SnO2 by weight. It is transparent and colorless in thin layers while in bulk form it is yellowish to grey...
(ITO) with high work function and a layer of low work function metal such as Al, Mg and Ca. The basic structure of such a cell is illustrated in Fig 2.
The difference of work function
Work function
In solid-state physics, the work function is the minimum energy needed to remove an electron from a solid to a point immediately outside the solid surface...
between the two conductors sets up an electric field in the organic layer. When the organic layer absorbs light, electrons will be excited to Lowest Unoccupied Molecular Orbital
Lumo
Lumo is a 2007 documentary film about twenty-year-old Lumo Sinai, a woman who fell victim to "Africa's First World War." While returning home one day, Lumo and another woman were gang-raped by a group of soldiers fighting for control of the Democratic Republic of the Congo during the 1994 Rwandan...
(LUMO) and leave holes in the Highest Occupied Molecular Orbital (HOMO) forming exciton
Exciton
An exciton is a bound state of an electron and hole which are attracted to each other by the electrostatic Coulomb force. It is an electrically neutral quasiparticle that exists in insulators, semiconductors and some liquids...
s. The potential created by the different work functions helps to separate the exciton pairs, pulling electrons to the positive electrode
Electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit...
(an electrical conductor used to make contact with a nonmetallic part of a circuit) and holes to the negative electrode. The current and voltage resulting from this process can be used to do work. Using electric fields is not the best way to break up excitons, heterojunction based cells which rely on effective fields are more effective.
Examples
Cells with phthalocyanine (Fig 1) as organic layer were investigated at the early stage. As early as 1958, Kearns et al. reported the photovoltaic effectPhotovoltaic effect
The photovoltaic effect is the creation of voltage or electric current in a material upon exposure to light. Though the photovoltaic effect is directly related to the photoelectric effect, they are different processes. In the photoelectric effect, electrons are ejected from a material's surface...
or the creation of voltage of a cell based on magnesium phthalocyanine
Phthalocyanine
Phthalocyanine 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...
a macrocyclic compound having an alternating nitrogen atom-carbon atom ring structure (MgPh), which had a photovoltage of 200mV. Ghosh et al. investigated the Al/MgPh/Ag cell, and obtained photovoltaic efficiency of 0.01% under illumination at 690 nm.
Conjugated polymers were also used in this type of photovoltaic cell. Weinberger et al. used polyacetylene (Fig 1) as the organic layer, Al and graphite as electrodes to fabricate a cell, which had an open circuit voltage of 0.3 V and a charge collection efficiency of 0.3%. Glenis et al. reported a Al/poly(3-nethyl-thiophene)/Pt cell had an external quantum yield of 0.17%, an open circuit voltage of 0.4V and a fill factor of 0.3. Karg et al. fabricated an ITO/PPV/Al cell, showing an open circuit voltage of 1V and a power conversion efficiency of 0.1% under white-light illumination.
Problems
In practice, single layer organic photovoltaic cells of this type do not work well. They have low quantum efficiencies (<1%) and low power conversion efficiencies (<0.1%). A major problem with them is the electric field resulting from the difference between the two conductive electrodes is seldom sufficient to break up the photogenerated excitons. Often the electrons recombine with the holes rather than reach the electrode. To deal with this problem, the multilayer organic photovoltaic cells were developed.Bilayer organic photovoltaic cells
Electron affinity
The Electron affinity of an atom or molecule is defined as the amount of energy released when an electron is added to a neutral atom or molecule to form a negative ion....
and ionization energy
Ionization energy
The ionization energy of a chemical species, i.e. an atom or molecule, is the energy required to remove an electron from the species to a practically infinite distance. Large atoms or molecules have a low ionization energy, while small molecules tend to have higher ionization energies.The property...
, therefore electrostatic forces are generated at the interface between the two layers. The materials are chosen properly to make the differences large enough, so these local electric fields are strong, which may break up the excitons much more efficiently than the single layer photovoltaic cells do. The layer with higher electron affinity and ionization potential is the electron acceptor, and the other layer is the electron donor. This structure is also called planar donor-acceptor heterojunctions.
Examples
C60 has high electron affinity, making it a good material as electron acceptor in photovoltaic cells of this type. Sariciftci et al. fabricated a C60/MEH-PPV double layer cell, which had a relatively high fill factor of 0.48 and a power conversion efficiency of 0.04% under monochromatic illumination. For PPV/C60 cells, Halls et al. reported a monochromatic external quantum efficiency of 9%, a power conversion efficiency of 1% and a fill factor of 0.48.Perylene derivatives are a group of organic molecules with high electron affinity and chemical stability. Ching W. Tang
Ching W. Tang
Ching W. Tang, is a Hong Kong - American Physical Chemist. He was born in Yuen Long, Hong Kong in 1947. Tang currently is the Doris Johns Cherry Professor in the Chemical Engineering Department, University of Rochester . He also has joint appointments in the Department of Chemistry and the...
deposited a layer of copper phthalcocyanine as electron donor and perylene tetracarboxylic derivative as electron acceptor, fabricating a cell with a fill factor as high as 0.65 and a power conversion efficiency of 1% under simulated AM2 illumination. Halls et al. fabricated a cell with a layer of bis(phenethylimido) perylene over a layer of PPV as the electron donor. This cell had peak external quantum efficiency of 6% and power conversion efficiency of 1% under monochromatic illumination, and the fill factor is up to 0.6.
Problems
The diffusion length of excitons in organic electronic materials is typically on the order of 10 nm. In order for most excitons to diffuse to the interface of layers and break up into carriers, the layer thickness should also be in the same range with the diffusion length. However, typically a polymer layer needs a thickness of at least 100 nm to absorb enough light. At such a large thickness, only a small fraction of the excitons can reach the heterojunction interface. To address this problem, a new type of heterojunction photovoltaic cells is designed, which is the dispersed heterojunction photovoltaic cells.Bulk heterojunction photovoltaic cells
Examples
C60 and its derivatives are also used as electron acceptor in the dispersed heterojunction photovoltaic cells. Yu et al. fabricated a cell with the blend of MEH-PPV and a methano-functionalized C60 derivative as the heterojunction, ITO and Ca as the electrodes. This cell showed a quantum efficiency of 29% and a power conversion efficiency of 2.9% under monochromatic illumination. Later they replaced MEH-PPV with P3OT, which obtained a cell with a quantum yield of 45% under a 10V reverse bias.Polymer/polymer blends are also used in dispersed heterojunction photovoltaic cells. Halls et al. used a blend of CN-PPV and MEH-PPV, fabricated a cell with Al and ITO as the electrodes, whose peak monochromatic power conversion efficiency is 1% and fill factor is 0.38.
Dye sensitized photovoltaic cells can also be considered as important ones of this type.
Graded Heterojunction photovoltaic cells
In this type of photovoltaic cell, the electron donor and acceptor are mixed together, like in the bulk heterojunction, but in such as way that the gradient is gradual. This architecture combines the short electron travel distance in the dispersed heterojunction with the advantage of the charge gradient of the bilayer technology.Examples
Holmes et al. fabricated a cell with a blend of CuPc and C60. The cell showed a quantum efficiency of 50% and a power conversion efficiency of 2.1% using 100 mW/cm2 simulated AM1.5G solar illumination for a graded heterojunction.Current challenges and recent progress
Difficulties associated with organic photovoltaic cells include their low quantum efficiency (~3%) in comparison with inorganic photovoltaic devices; due largely to the large band gap of organic materials. Instabilities against oxidation and reduction, recrystallization and temperature variations can also lead to device degradation and decreased performance over time. This occurs to different extents for devices with different compositions, and is an area into which active research is taking place.Other important factors include the exciton diffusion length; charge separation and charge collection; and charge transport and mobility, which are affected by the presence of impurities.
Effect of film morphology
Heterojunction
A heterojunction is the interface that occurs between two layers or regions of dissimilar crystalline semiconductors. These semiconducting materials have unequal band gaps as opposed to a homojunction...
of donor-acceptor organic materials have high quantum efficiency compared to the planar hetero-junction, because it is more likely for an exciton to find an interface within its diffusion length. Film morphology can also have a drastic effect on the quantum efficiency of the device. Rough surfaces and presence of voids can increase the series resistance and also the chance of short circuiting. Film morphology and as a result quantum efficiency can be improved by annealing of a device after covering it by ~1000Å thick metal cathode. Metal film on top of the organic film applies stresses on the organic film, which helps to prevent the morphological relaxation in the organic film. This gives more densely packed films while at the same time allows the formation of phase-separated interpenetrating donor-acceptor interface inside the bulk of organic thin film.
Controlled growth heterojunction
Charge separation occurs at the donor acceptor interface. Whilst traveling to the electrode, a charge can become trapped and/or recombine in a disordered interpenetrating organic material, resulting in decreased device efficiency. Controlled growth of the heterojunction provides better control over positions of the donor-acceptor materials, resulting in much greater power efficiency (ratio of output power to input power) than that of planar and highly disoriented hetero-junctions (as shown in Fig 5(a), (b)). Thus, the choice of suitable processing parameters in order to better control the structure and film morphology is highly desirable.Progress in growth techniques
Mostly organic films for photovoltaic applications are deposited by spin coatingSpin coating
Spin coating is a procedure used to apply uniform thin films to flat substrates. In short, an excess amount of a solution is placed on the substrate, which is then rotated at high speed in order to spread the fluid by centrifugal force...
and vapor-phase deposition. However each method has certain draw backs, spin coating technique can coat larger surface areas with high speed but the use of solvent for one layer can degrade the already existing polymer layer. Another problem is related with the patterning of the substrate for device as spin-coating results in coating the entire substrate with a single material.
Vacuum thermal evaporation
Organic vapor phase deposition
Organic thin film grown from "Organic vapor phase deposition" (OVPD) is proven to give better control on the structure and morphology of the film than vacuum thermal evaporation. The process involves evaporation of the organic material over a substrate in the presence of an inert carrier gas. Resulting film morphology can be changed by changing the gas flow rate and the source temperature. Uniform film can be grown by reducing the carrier gas pressure, which will increase the velocity and mean free path of the gas, and as a result boundary layer thickness decreases. Cells produced by OVPD do not have issues related with contaminations from the flakes coming out of the walls of the chamber, as the walls are warm and do not allow molecules to stick to and produce a film upon them.Another advantage over VTE is the uniformity in evaporation rate. This occurs because the carrier gas becomes saturated with the vapors of the organic material coming out of the source and then moves towards the cooled substrate, Fig6(b). Depending on the growth parameters (temperature of the source, base pressure and flux of the carrier gas) the deposited film can be crystalline or amorphous in nature. Devices fabricated using OVPD show a higher short-circuit current density than that of devices made using VTE. An extra layer of donor-acceptor hetero-junction at the top of the cell may block excitons, whilst allowing conduction of electron; resulting in improved cell efficiency.
Organic solar ink
PlextronicsPlextronics
Plextronics, Inc. is an international technology company that specializes in printed solar, lighting and other electronics. Headquartered in Pittsburgh, Pennsylvania, the company's focus is on organic solar cell and organic light-emitting diode lighting, specifically the conductive inks and process...
Plexcore PV 2000 organic solar ink is able to deliver higher performance in fluorescent lighting conditions in comparison to amorphous silicon
Amorphous silicon
Amorphous silicon is the non-crystalline allotropic form of silicon. It can be deposited in thin films at low temperatures onto a variety of substrates, offering some unique capabilities for a variety of electronics.-Description:...
solar cells, and said to have a 30% to 40% increase in indoor power density in comparison to the standard organic solar technology.
Plextronics has also developed a manufacturing method that allows for low-temperature processing of OPV. While previous industry standard techniques required a glass substrate to be annealed
Annealing (metallurgy)
Annealing, in metallurgy and materials science, is a heat treatment wherein a material is altered, causing changes in its properties such as strength and hardness. It is a process that produces conditions by heating to above the recrystallization temperature, maintaining a suitable temperature, and...
at temperatures at or above 110° C, this method enables annealing at less than 65° C. It is expected to reduce manufacturing costs as it may enable the use of less expensive substrates, especially once the process is transferred to flexible substrates such as 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...
.
See also
- BioplasticBioplasticBioplastics are a form of plastics derived from renewable biomass sources, such as vegetable fats and oils, corn starch, pea starch, or microbiota, rather than fossil-fuel plastics which are derived from petroleum...
- Conductive inkConductive ink'Conductive ink' is an ink that conducts electricity.These materials may be classed as fired high solids systems or PTF polymer thick film systems that allow circuits to be drawn or printed on a variety of substrate materials such as polyester to paper...
- Dye-sensitized solar cell
- Energy harvestingEnergy harvestingEnergy harvesting is the process by which energy is derived from external sources , captured, and stored for small, wireless autonomous devices, like those used in wearable electronics and wireless sensor networks.Energy harvesters...
- Grid parityGrid parityGrid parity is the point at which alternative means of generating electricity is at least as cheap as grid power.For solar energy, it is achieved first in areas with abundant sun and high costs for electricity such as in California, Hawaii, Spain and Japan. Many solar power advocates predict that...
- Hybrid solar cellHybrid solar cellHybrid solar cells combine advantages of both organic and inorganic semiconductors. Hybrid photovoltaics have organic materials that consist of conjugated polymers that absorb light as the donor and transport holes. Inorganic materials in hybrid cell are used as the acceptor and electron...
- Nanocrystal solar cellNanocrystal solar cellQuantum dot solar cells are an emerging field in solar cell research that uses quantum dots as the photovoltaic material, as opposed to better-known bulk materials such as silicon, copper indium gallium selenide or CdTe. Quantum dots have bandgaps that are tunable across a wide range of energy...
- Photoelectrochemical cellPhotoelectrochemical cellPhotoelectrochemical cells or PECs are solar cells which generate electrical energy from light, including visible light. Some photoelectrochemical cells simply produce electrical energy, while others produce hydrogen in a process similar to the electrolysis of water.-Photogeneration cell:In this...
- Polymer solar cellPolymer solar cellPolymer solar cells are a type of flexible solar cell. They can come in many forms including: organic solar cell , or organic chemistry photovoltaic cell that produce electricity from sunlight using polymers. There are also other types of more stable thin-film semiconductors that can be deposited...
- Printed electronicsPrinted electronicsPrinted electronics is a set of printing methods used to create electrical devices on various substrates. Printing typically uses common printing equipment or other low-cost equipment suitable for defining patterns on material, such as screen printing, flexography, gravure, offset lithography and...
- Roll-to-roll
Further reading
- Electronic Processes in Organic Crystals and Polymers, 2 ed. by Martin Pope and Charles E. Swenberg, Oxford University Press (1999), ISBN 0195129636
- Organic Photovoltaics by Christoph Brabec, Vladimir Dyakonov, Jürgen Parisi and Niyazi Serdar Sariciftci (eds.), Springer Verlag (Berlin, 2003), ISBN 3-540-00405-X
- Organic Photovoltaics: Mechanisms, Materials, and Devices (Optical Engineering) by Sam-Shajing Sun and Niyazi Serdar Sariciftci (eds.), CRC Press (2005), ISBN 0-8247-5963-X
- Handbook of Organic Electronics and Photonics (3-Volume Set) by Hari Singh Nalwa, American Scientific Publishers. (2008), ISBN 1-58883-095-0
- Progress in Photovoltaics: Research and Applications, Volume 18, Issue 5, Solar Cell Efficiency Tables (version 36), Wiley 2010