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Photovoltaics

This lecture complements chapter 3 inRenewable Energy

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Silicon lattice with electron pairs (dots)

in covalent bonds (lines)

The atoms in crystalline solids are held together in a regular lattice by covalentbonds. Each covalent bond linking two atoms consists of a pair of electrons,

called valence electrons, one from each atom. The valence electrons move inthe space between the two atoms with energies in a band of energies known asthe valence band. The valence band of a solid consists of a large number ofseparate energy levels, one for each valence electron. The behavior of electronsis such that when all the valence electrons are in position no more valence

electrons can be added to the lattice.

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Electron energy level bands in solids

In some solids there are extra electrons moving freely through the lattice withoutbeing held in covalent bonds. These electrons are called conduction electronsbecause they carry electric currents through the solid. Their energies are inanother band known as the conduction band at a higher energy level than the

valence band. Between the highest energy level in the valence band and thelowest energy level in the conduction band there may be a forbidden band of

energies. No electrons can have energies within the forbidden band. Thedifference between the energy at the bottom of the conduction band and theenergy at the top of the valence band is called the energy gap. The mostconvenient measure of energy in electronics is the energy gained by an electron

when it is accelerated through an electric potential of one volt, called the electronvolt (eV). Energy gaps are typically of the order 1 eV = 1.60210-19J.

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Electron energies in an electrical

insulator

An electrical insulator has its valence band filled with electrons and its

conduction band empty. Therefore, there are no free electrons available tocarry an electric current. Moreover, the energy gap is large, so it is notpossible for ordinary processes to provide enough energy for the valenceelectrons to break out of their valence bonds and jump into the conductionband where they might carry an electric current. Carbon in the form of

diamond is an insulator with energy gap 5.5eV

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Electron energies in an electrical

conductor

An electrical conductor, such as copper, besides having its valence

band filled, also has a partly filled conduction band. Sometimes thereis no forbidden band because the conduction and valence bandsoverlap. The conduction band has empty energy levels into which theconduction electrons can jump with very little change of energy.Consequently, the conduction electrons are free to move through the

lattice and carry an electric current.

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Electron energies in a semiconductor

An intrinsic semiconductor is a pure substance with just enough electrons

to fill the valence band, but it has a small energy gap. It is possible forcertain processes to give some valence electrons enough energy to jumpacross the energy gap into the conduction band where they are able tocarry an electric current. As there are only a few of these conductionelectrons the solid is called a semiconductor. An example is silicon, whichhas an energy gap of 1.1 eV.

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Electron-hole pairs in semiconductors When an electron jumps from the valence band to the conduction

band it leaves behind a hole, or missing electron, in a covalent bond.This hole can easily be filled by an electron from an adjacent covalentbond, so the hole can move through the lattice.

Thus an intrinsic semiconductor conducts electricity by means ofnegative charge carriers (electrons) and positive charge carriers (holes).

Electron-hole pairs may be produced by thermal excitation. Thenumber of pairs produced depends on the energy gap Eg and on themagnitude ofkT, where Tis the absolute temperature and k isBoltzmann's constant 8.61710-5 eV/K. At ordinary temperatures T=300K, and so kT=0.026 eV. This is only 2.4% ofE

gfor silicon, but

it is enough to give some conductivity.

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Photon excitation of electron-hole pairs Electron-hole pairs may also be produced by photon excitation. The

rate at which pairs are produced depends on the intensity of the light,

i.e. the rate at which photons are absorbed. A photon can create an electron-hole pair only if its energy is equal

to, or greater than, the energy gap. The energy of a photon is given byhc/, where c is the speed of light. When lambda is given in m andthe photon energyE

is given in eV we have E

= 1.24/. For photon excitation in silicon (Eg = 1.1 eV) we require E > 1.1 eV,

i.e. < 1.13 m. Therefore, the photons in visible light can increasethe electrical conductivity of silicon by the creation of electron-holepairs, but the photons in the infra-red part of the spectrum with

lambda > 1.13 m cannot. The electrical conductivity of semiconductors can be greatly increasedby adding certain impurities in concentrations of about one part permillion. The process is called doping.

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n-type doped semiconductor

Silicon may be doped with phosphorous atoms, which have five outerelectrons. Four of the outer electrons become valence electrons in the valence

band. The energy levels of the extra electrons are just below the bottom of theconduction band with a small energy gap of 0.05 eV. This is less than twice the

value ofkT(0.026 eV) at a temperature 300K. Therefore the extra electrons areeasily excited thermally into the conduction band where they become negative

charge carriers.

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Majority and minority charge carriers

The number of conduction electrons donated bythe impurities is much greater than the number ofcharge carriers produced from electron-hole pairs.

The donated conduction electrons are thereforecalled majority carriers. The charge carriers produced from the electron-

hole pairs are called minority carriers. Because the majority carriers are negative thephosphorous-doped silicon crystal is called an n-

type semiconductor.

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Comparison metallic conductor, pure

silicon, and doped silicon In a typical metallic conductorthe density of

electrons in the half-filled conduction band isabout 1028m-3. In pure silicon the density of the electrons thermally

excited into the conduction band as minoritycarriers is about 1010m-3.

In doped silicon the number of impurity atoms maybe about 1022m-3. The number of electrons

thermally excited into the conduction band asmajority carriers from the energy levels of the extraelectrons is then about 1020m-3.

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p-type doped semiconductors

Silicon may also be doped with boron atoms, which have only three outer

electrons. These atoms create unfilled energy levels just above the top of thevalence band . Electrons are easily excited thermally into these levels, leavingholes in the valence band. The holes created in this way act as positivemajority charge carriers, and the doped crystal is called a p-type semiconductor.

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Charge balance In each type of semiconductor the electric charges

on the fixed impurities balance the charges on themajority carriers and keep the crystal as a wholeelectrically neutral. Thus, in n-type material the

impurities act as fixed positive charges, and in p-type material the impurities act as fixed negativecharges.

However, at a junction between an n-type and a p-type semiconductor there can a local imbalance ofspace charge, giving rise to a local electric field.

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Semiconductor n-p junctions

An n-p junction is a semiconductor whichis doped as an n-type semiconductor on

one side and as a p-type semiconductor onthe other side. Near the junction, freeelectrons from the n-type side fill the holesfrom the p-type side forming a depletionlayer which is deficient in majority carriers.

In this layer the fixed impurities then create an excess positive charge on then-type side and an excess negative charge on the p-type side. This produces

an electric potential barrier Vbwhich counterbalances further movement ofmajority carriers across the junction. The height of the potential barrier Vbis somewhat less than the energy gap Eg because the fixed impurities slightlyhinder the movement of majority carriers. The potential difference across

the junction produces an electric field in the depletion layer directed fromthe n-type side towards the p-type side.

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The minority current across an

n-p junction When equilibrium has been reached in an n-p junction there are two

equal and opposite electric currents flowing across the depletionlayer. One current consists of minority carriers, and the other currentconsists of majority carriers.

Consider first the minority carriers. The thermally excited electronswhich are minority carriers on the p-side of the junction are caused to

drift towards the n-type side by the electric field in the depletionlayer. Likewise, the holes which are minority carriers on the n-type side of

the junction are caused to drift towards the p-type side. The effect of these two movements is a small drift current I

minfrom

the n-type side to the p-type side. The size ofImin depends only on therate at which minority carriers are being created by thermal excitations ofelectrons across the energy gap Eg of the semiconductor. It does notdepend on the height Vb of the potential barrier.

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The majority current across an

n-p junction In the equilibrium state the current Imin caused by minority

carriers is balanced by an equal and opposite current Imaj caused

by the diffusion of majority carriers. Because there are more electron carriers on the n-type side than

on the p-type side, there is a diffusion of electrons across the

junction from the n-type side to the p-type side. Likewise, there is a diffusion of holes across the junction from

the p-type side to the n-type side.

The effect of these two movements is the diffusion current Imaj

,which is small because it is against the potential barrier. Thenumber of fixed impurity charges in the depletion layer adjustsitself so that the height Vb of the potential barrier allows only

enough majority carriers across to make Imaj balance Imin.

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Junction diode with reverse biasWhen an external potential difference is applied

across the junction the height of the potentialbarrier is changed. This causes Imaj to change,because the majority carriers have to diffuse againsta stronger electric field. But Imin is still limited by

the thermal excitation of electron-hole pairs, andremains the same. If the positive terminal of a battery is connected tothe n-type side of the junction, then the height ofthe potential barrier is increased. This is calledreverse bias. With reverse bias Imaj is reduced, andonly the very small current Imin flows in the circuit.

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Junction diode with forward bias

If the positive terminal of the battery isconnected to the p-type side of thejunction then the height of the potentialbarrier is reduced. This is called forward

bias. With forward bias Imin is stillunchanged, but Imaj is increased, becausethe majority carriers diffuse against a

weaker electric field.

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Current-voltage characteristic of a

junction diode

The current-voltage characteristic curve ofa junction diode is shown in the figure. It is highly non-linear, so the diode acts asa rectifier and does not obey Ohm's law. With reverse bias the diode has a high

resistance. With forward bias the diode hasa low resistance, and the resistance decreasesas the forward bias is increased.

If the applied forward bias voltage is large enough the internal electricfield across the depletion layer is from the p-type side of the junction tothe n-type side. Then a large current flows in the circuit.

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Photovoltaic solar cell circuit

When solar radiation falls on a silicon n-p junction, photons withwavelength less than 1.13 m generate electron-hole pairs. The electricfield in the depletion layer drives the electrons to the n-type side and theholes to the p-type side. This separates most of the electrons and holesbefore they can recombine. A solar photovoltaic cell consists of a thick

n-type crystal covered by a thin p-type layer exposed to the sunlight. Anelectrical load resistance R is connected across the junction. Theelectrons and holes produce a current, and the energy in the solarradiation is converted into electrical energy in the circuit.

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Current-voltage characteristics of a

photovoltaic solar cell Electron-hole pairs generated in a photovoltaiccell by the absorption of photons increase thenumber of minority carriers on both sides of then-p junction. This causes the current Imin of minoritycarriers to increase. But the current Imaj of the

majority carriers remains the same. The increase in the number of minoritycarriers causes the current-voltage characteristicof the photovoltaic cell to shift downwards as

shown in the figure. The current-voltage characteristic curvespublished by the manufacturers of photovoltaiccells are upside down copies of the bottom righthand quadrant of the figure.

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Solar cell with resistive load

If the external load resistance R is zero we have a short circuit, and thecurrent in the circuit is I = Imin - Imaj, where Imaj is constant, and Imin isproportional to the rate at which electron-hole pairs are created by the

absorption of photons. This is proportional to the intensity of the lightfalling on the photovoltaic cell.

When the load resistance R is increased an increasing forward bias V= IR isapplied to the junction. This lowers the potential barrier, which increases

Imaj, and the current I is reduced. When the load resistance is infinite we have an open circuit, and the voltage

across the photovoltaic cell is about 0.6V, which is determined by the heightof the internal potential barrier Vb. The electrical power in the load

resistance is zero in a short circuit (R = 0), and also in an open circuit (R =infinity). The maximum power is obtained when the potential drop acrossthe load is about 80% ofVb, which is about 0.5V in silicon solar cells.

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The current-voltage characteristic and

maximum-power point A solar cell may operate over a wide range of voltages (V) and

currents (I). By increasing the resistive load on an irradiated cell

continuously from zero (a short circuit) to a very high value (anopen circuit) one can determine the maximum power point, thepoint that maximizes VI; that is, the load for which the cell candeliver maximum electrical power at that level of irradiation.

(The output power is zero in both the short circuit and opencircuit extremes).

A high quality, monocrystalline silicon solar cell, at 25 C cell

temperature, may produce 0.60 volts open-circuit (Voc). The celltemperature in full sunlight, even with 25 C air temperature,will probably be close to 45 C, reducing the open-circuitvoltage to 0.55 volts per cell. The voltage drops modestly, with

this type of cell, until short-circuit current is approached (Isc).

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Dependence of current and voltage on

intensity of illumination Maximum power (with 45 C cell temperature) is typically

produced with 75% to 80% of the open-circuit voltage (0.43volts in this case) and 90% of the short-circuit current. Thisoutput can be up to 70% of the Voc Isc product.

The short-circuit current (Isc) from a cell is nearly proportional

to the illumination, while the open-circuit voltage (Voc) maydrop only 10% with a 80% drop in illumination.

Lower-quality cells have a more rapid drop in voltage with

increasing current and could produce only Voc at Isc. Theusable power output could thus drop from 70% of the Voc Iscproduct to 50% or even as little as 25%. Vendors who rate theirsolar cell power only as Voc Isc , without giving load curves,

can be seriously distorting their actual performance.

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Efficiency of a solar cell The efficiency of photovoltaic conversion is limited by the relationships

between the photon energies and the energy gap in the semiconductor.

Photons in the ultra-violet and visible regions of the solar spectrum haveenergies greater than the energy gap, so only part of their energy is convertedinto electrical energy by the creation of electron-hole pairs. The excess energyis dissipated as heat.

Photons in the near infra-red with wavelengths 0.7 m to 1.1 m haveenergies only slightly greater than the energy gap, so most of their energy isconverted into electricity.

Near infra-red photons with wavelengths greater than 1.13 m have energiesless than the energy gap and cannot produce electron-hole pairs, so theycannot contribute to the electrical energy output of the solar cell. Takingthese facts into consideration we find that an upper limit to the efficiency ofa silicon solar cell is 45%.

However, recombination of electrons and holes before they are completely

separated reduces the attainable efficiency still further to about 20%.

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How to measure efficiency? A solar cell's energy conversion efficiency is

This term is calculated using the ratio of the maximum power point Pmdivided by the input light irradiance (E, in W/m) under standard testconditions (STC) and the surface area of the solar cell (Ac in m).

STC specifies a temperature of 25C and an irradiance of 1000 W/m withan air mass 1.5 (AM1.5) spectrum. These correspond to the irradiance andspectrum of sunlight incident on a clear day upon a sun-facing 37-tiltedsurface with the sun at an angle of 41.81 above the horizon.

This condition approximately represents solar noon near the spring andautumn equinoxes in the continental United States with surface of the cellaimed directly at the sun. Thus, under these conditions a solar cell of 12%efficiency with a 100 cm2 (0.01 m2) surface area can be expected to produce

approximately 1.2 watts of power.

=Pm

E Ac

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Three generations of solar cells Solar Cells are classified into three generations which

indicates the order of which each became prominent.At present there is concurrent research into all threegenerations while the first generation technologies aremost highly represented in commercial production,

accounting for 89.6% of 2007 production.

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First generation solar cells First generation cells consist oflarge-area, high quality

and single junction devices. First Generation technologiesinvolve high energy and labor inputswhich prevent anysignificant progress in reducing production costs. Single

junction silicon devices are approaching thetheoretical limiting efficiency of 33%, and can achievecost parity with fossil fuel energy after a payback

period of 5-7 years.

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First generation silicon technologies Monocrystalline silicon (c-Si): often made using the Czochralski

process. Single-crystal wafer cells tend to be expensive, and

because they are cut from cylindrical ingots, do notcompletely cover a square solar cell module without asubstantial waste of refined silicon. Hence most c-Si panelshave uncovered gaps at the four corners of the cells.

Poly- or multicrystalline silicon (poly-Si or mc-Si): made from castsquare ingots large blocks of molten silicon carefully cooledand solidified. These cells are less expensive to produce thansingle crystal cells but are less efficient.

Ribbon silicon: formed by drawing flat thin films from moltensilicon and having a multicrystalline structure. These cellshave lower efficiencies than poly-Si, but save on productioncosts due to a great reduction in silicon waste, as thisapproach does not require sawing from ingots.

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Second generation technologies Second generation materials have been developed to address energy

requirements and production costs of solar cells. Alternative

manufacturing techniques such as vapor deposition andelectroplating are advantageous as they reduce high temperatureprocessing significantly. It is commonly accepted that asmanufacturing techniques evolve production costs will be dominatedby constituent material requirements, whether this be a silicon

substrate, or glass cover. Second generation technologies are expected to gain market share in2008. The most successful second generation materials have beencadmium telluride (CdTe), copper indium gallium selenide (CIGS),amorphous silicon (a-Si), and micromorphous silicon. These

materials are applied in a thin film by standard plasma enhancedchemical vapor deposition (PECVD) to a supporting substrate such asglass or ceramics reducing material mass and therefore costs.

These technologies do hold promise of higher conversion efficienciesand cheaper production costs. Among major manufacturers there iscertainly a trend toward second generation technologies.

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Combining cells with different bandgap

The efficiency of a solar cell can beenhanced by combining cellsconsisting of different semiconductors

with different bandgaps, and thusprovide absorption of a larger portionof the solar light spectrum.

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Amorphous silicon (a-Si) a-Si is the non-crystalline form of silicon. Silicon is normally

tetrahedrally bonded to four neighboring silicon atoms. In crystallinesilicon this tetrahedral structure is continued over a large range,forming a well-ordered lattice (crystal).

In a-Si this long range order is not present and the atoms form acontinuous random network. One of the main advantages over c-Sirelies in its production technique, as thin films of it can be deposited

over large areas. It can be doped to form p- or n-type layers to form electronic devices.

For this reason a-Si has become the material of choice for the active

layer in thin-film transistors (TFTs), which are used in large-areaelectronics applications, mainly for liquid-crystal displays (LCDs).

It is also used to produce large-area photovoltaic solar cells. This is arelatively new application, although the small solar cells used in

some pocket calculators have been made with a-Si for many years.

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Cadmium-telluride (CdTe) cells CdTe is a highly useful material in the making of solar cells,

which provides a highly cost-effective solar cell design, but at a

lower efficiency than polysilicon. However, this is easily off-set by the ability of CdTe panels to

handle normally problematic low-light scenarios efficiently-substantially more efficiently than traditional X-si panels.

Cadmium telluride is toxic but only so if ingested, its dustinhaled, or if it is handled improperly. Once properly andsecurely captured and encapsulated, CdTe used in

manufacturing processes may be rendered harmless. The disposal life-cycle and long term safety of cadmium

telluride is becoming more of a known issue in the large scale

commercialization of cadmium telluride solar panels.

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Copper indium gallium selenide (CGIS) CIGS is a new semiconductor material. The material is a solid

solution of copper indium selenide (CIS) and copper galliumselenide (CGS), with a chemical formula CuInxGa(1-x)Se2,

where the value of x can vary from 1 to 0 (pure CIS to CGS). It is a tetrahedrally-bonded semiconductor, with a bandgap

varying continuously with x from about 1.0eV (for CIS) toabout 1.7eV (for CGS).

Its main use is in the form of polycrystalline thin films. Unlikesilicon cells the structure of CIGS is a more complexheterojunction system. The best efficiency achieved as of

December 2005 was 19.9%. This efficiency is by far the highestcompared with those achieved by other thin film technologiessuch as cadmium-telluride (CdTe) or amorphous silicon (a-Si).

As for CIS, and CGS solar cells, the world record total areaefficiencies are 15.0% and 10.2% respectively.

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An example of a multi-bandgap cell

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Commercialization of second

generation solar cells However commercialization of these technologies has proven difficult.

Significant cost reduction requires mass production, which is hard to

implement as long as the technologies are not cost competititive. In 2007 First Solar produced 200 MW of CdTe solar cells making it the fifth

largest producer of solar cells in 2007 and the first ever to reach the top 10from production of second generation technologies alone.

Wurth Solar commercialized its CIS technology in 2007 producing 15 MW. Nanosolar commercialized its CIGS technology in 2007 with a production

capacity of 430 MW for 2008 in the USA and Germany.

In 2007 CdTe production represented 4.7% of total market share, thin film

silicon 5.2% and CIGS 0.5%.

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Towards a third generation First-generation solar cells are built using a clean-

room process that's practically identical to the onefor computer CPUs.

Second-gen solar technology places a silicon filmon glass or plastic and uses only about 1 percent of

the silicon of the older units per watt generated. But these energy-efficient panels are really only

cost-effective in large-scale deployment, because

their vacuum-based production process, typicallyplasma enhanced chemical vapor deposition(PECVD), is quite susceptible to manufacturingglitches.

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Third (?) generation technologies Instead of growing and slicing silicon ingots, or vacuum-based glass

etching, specialized printers spew nanoparticles onto rolls of thin,

flexible material through ink jet printing technology, aluminum foil,and space-age chemical compounds. Third-gen solar factories createpanels for a fraction of the cost of earlier generations: as little as $1per watt, compared with around $4.50 for traditional solar cells.That's roughly equivalent to using fossil fuels.

Even though the efficiency of these new thin solar panels is lower than thatof previous generations, their incrediblycheap price, coupled with theirflexible nature, will usher in much wider use of solar power.

The Nanosolar corporation hopes to revolutionize power generationby enabling a 10-megawatt real breakthrough has appeared with

solar's third-gen technology: thin-film solar solar power plant tobloom in under a year, as opposed to the ten years needed to build atraditional coal, gas, or nuclear plant.

M b d f f h d

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More ambitious definition of third

generation Some actors in the field consider third generation solar cells as just

a research target, and that they do not really exist yet.

According to this view, the goal of third generation solar cellresearch are low-cost, high efficiency cells. The goal is thin-film cellsthat use novel approaches to obtain efficiencies in the range of 30-60%.

Some analysts predict that third generation cells could start to becommercialized sometime around 2020, but this is just a guess. Technologies associated with third generation solar cells include

multijunction photovoltaic cells, tandem cells, nanostructuredcells to better pick up incident light, and using excess thermalgeneration to enhance voltages or carrier collection.

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The use of nanotechnologyThe ability to architect and assemble

materials on a nanometer scale nowmakes it possible to optimize solarcells at the very length scale at whichthe relevant photovoltaic

semiconductor quantum-physicsoccurs. Molecular self-assemblytechniques for instance now giveunprecedented capability of designingand creating nanostructured materialswith novel properties.

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Printing of nanofilms The absorber (semiconductor) isthe most critical layer of a solar cell. Athin film of CIGS can simply be

printed (solution-coated) to create anefficient solar cell. Conventionally, CIGS thin-film solar

cells have been fabricated withvacuum deposition techniques suchas sputtering or evaporation, but theprocess cost of these techniques is sohigh that the result is not aninexpensive cell.

Printing is by far the simplest andmost robust technique for depositingthin films. But, of course, this wouldrequire a CIGS ink to print, and sucha breakthrough ink, composed ofnanoparticles of CIGS material,

would require solving an entire array

of fundamental science challenges.

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Future possibilities The new materials that solar energy can be harnessed with is

one of the most exciting elements of the new technology.

The flexible and lightweight physical characteristics of thedifferent types of third generation solar cells makes manynew applications possible.

There is the possibility that solar cells could be integrated

into clothing which would allow us to have personal wirelesspower without batteries. Another plausible application could be a type of automobile

paint that is blended with polymer solar cells. This could

help maintain the lightweight form of a solar car while stillproviding ample energy to power it.

I i f l ll i

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Integration of solar cells into

solar panels Photovoltaic cells typically require protectionfrom the environment. For cost and practicality

reasons a number of cells are connectedelectrically and packaged in a photovoltaicmodule.A collection of these modules that are

mechanically fastened together, wired, anddesigned to be a field-installable unit, sometimeswith a glass covering and a frame and backingmade of metal, plastic or fiberglass, are knownas a photovoltaic panel or simply solar panel.A photovoltaic installation typically includesan array of photovoltaic modules or panels, aninverter, batteries (for off grid) andinterconnection wiring.

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Norwegian solar cell effort The Norwegian solar energy companyRenewable

Energy Corporation (REC) is unique in that itdelivers goods and services in the whole valuechain for solar energy. REC is the worlds

largest producer of solar grade silicon andwafers, and a considerable producer of solarcells and modules. The company has over 1 000employees, and the activity is divided into threedivisions:

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Renewable Energy Corporation (REC) REC Silicon is the worlds largest producer of solar grade polysilicon

for the photoelectrical industry. The production is carried out at twofactories in the U.S., and the company is establishing a new large

factory in the U.S. that will use a new and patented technology forthe production of granulated polysilicon through the FBR process(Fluidized Bed Reactor), that gives a more cost-efficient productionthan earlier.

REC Waferis the worlds largest producer of multi-crystalline wafers

for the solar cell industry. The production is carried out at factoriesin Glomfjord and Herya in Norway. The company is also starting anew factory at Herya that will double the production capacity to 550MWp. The company also has its own factory that produces mono-crystalline blocks for wafer-production in Glomfjord. This factory has

a production capacity of 25 MWp. REC Solarproduces solar cells in Narvik in Norway and solar cell

modules at Glava in Sweden. The company today has a totalproduction capacity of 45 MWp, but is extending the production to225 MW

pcells and 100 MW

pwith modules. The company also has

an operation for installation of small scale systems in South-Africa.

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Elkem Solar The Norwegian industry group

Elkem ventures into solar energythrough the company Elkem Solar.

Elkem has been involved inresearch and technologydevelopment related to solar gradesilicon since the beginning of the1980s. Through the long

experience and broad competenceon metallurgic processes, thecompany has developed a methodfor producing polycrystallinesilicon.

The method is simpler and lesscostly than the Siemens-process,but doesnt provide as cleansilicon. However, tests have shownthat the material can be used insolar cells and achieve an

efficiency of 18 per cent.

Elkem Solar has decided to invest 330million in a new factory at Elkem

Fiskaa in Kristiansand. The plant willhave an annual production capacity of5000 tons of clean silicon and employsome 150 people when it is completed inthe middle of 2008.

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A new producer of wafers Norsun The Norwegian Company Norsun produces monocrystalline

silicon ingots and wafers. The company was founded in 2005

by Alf Bjrseth, who was also behind the establishment ofREC. Monocrystalline silicon wafers give solar cells with a higher

efficiency than multicrystalline. The silicon wafers are sold to

players in the international solar energy market forprocessing to solar cells and solar panels. The company establishes production plants in rdal with a

production capacity of 130 MW. Norsun will also invest in

the production of the raw material in itself, polysilicon, andwithin second generation solar energy based on thin filmtechnology.

Solar cell research at Institute of Energy

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Solar cell research at Institute of Energy

Technology (IFE) IFE has recently been granted MNOK 31 by the Research

Council of Norways NANOMAT program. With this

funding IFE will start up an institution-based strategic projecton the solar cell technology of the future. The grant ensures IFEs leading position in Norway in

photovoltaic research.The project Thin and highly efficient

silicon-based solar cells incorporating nanostructures represents animportant step forward for IFEs photovoltaic activities. The aim of the project is developing new technology and

new, nanostructured materials for solar cells with a

significantly higher efficiency than previously achieved. Byemploying these kinds of materials, in principle, one canmake more efficiently use of all the energies innate in thesolar spectrum. This type of technology is often referred to asthird generation solar cells, and is a big and active field of

research around the world.

Nordic Centre of Excellence in

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Nordic Centre of Excellence in

Photovoltaics The Nordic region has in recent years experienced the introduction

and fast expansion of a solar electricity industry. In order to secure thecontinued expansion of this industry, a strong Nordic R&D platform isrequired.

Nordic Centre of Excellence in Photovoltaics consists of 7 differentresearch organizations within the Nordic region doing research onsolar cells; Institute for Energy Technology (IFE), Danish

Technological Institute, Helsinki University of Technology,Norwegian University of Science and Technology, UppsalaUniversity, Ioffe Physico-Technical Institute in St. Petersburg, andTallinn University of Technology.

To turn the network into a virtual centre,five cross disciplinary researchtopics of common interest for all the groups involved in the centrehave been defined: Search for new materials, Encapsulation andlifetime of solar panels, 3D modelling of solar cell structures,Contacting of solar cells, and light collection/light trapping. Thesetopics will serve as cornerstones in the new project.

Nordic PV - Solar Electricity from

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y

Materials to System Integration The purpose ofNordic PV, a scientific project between Institute forEnergy Technology (IFE), University of Uppsala (UU), HelsinkiUniversity of Technology (HUT), Danish Technological Institute

(DTI) Norwegian University of Science and Technology (NTNU)funded by Nordic Energy Research, is to stimulate research anddevelopment related to solar electricity in order to strengthen thecommercial development of solar cells in the Nordic countries.

Already, several Nordic companies are visible in the international

solar electricity market, including NAPS Systems Oy, RautaruukkiOy, Endeas Oy, Gaia Solar A/S, Topsil A/S, Elkem Solar AS,ScanWafer ASA, ScanCell AS, SolEnergy AS, SiTech AS, RenewableEnergy Corporation AS, ScanModule AB, Gllivare Photovoltaic AB,

Arctic Solar AB and Solibro AB.

There is no reason why these companies may not maintain theirmarket share in the coming years. Even using conservative scenariosof growth within the solar cell industry there is a large potential forindustry development in the Nordic counties. However in order tomake this happening, it is important for the companies to havepresence qualified R&D personnel within the Nordic region.

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Growth in world PV markets

Source: IEA PVPS report 2009

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Growth in world PV markets

Source: IEA PVPS report 2009

h ld k

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Growth in world PV markets

Source: IEA PV roadmap

PV h l d

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PV technology trends

Crystalline silicon (single and multi crystalline) 2006: 91% of marked

2007: 87% of marked 2008: 78% of marked

Thin film technologies have taken marked shares Improvements in efficiencies Usability on flexible substrates

New technologies as nanostructured thin films and silicon anddye-sensitized solar cells have a low share today, but areexpected to grow substantially in the near future.

Cell supply shortage still limits the module production

Nobel prize in Physics 2010:

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October 5th, 2010:

http://www.kva.se/en/

http://www.solarnovus.com/index.php?view=article&id=1454

Nobel prize in Physics 2010:

Graphene

Instructive videos from YouTube

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Instructive videos from YouTube

(there are many more) PV basics

http://www.youtube.com/watch?v=qYeynLy6pj8 http://www.youtube.com/watch?v=caeEyhJZnTs&feature=related

Freiburg solar village http://www.youtube.com/watch?v=IMnB6V5yG1I&feature=related http://www.youtube.com/watch?v=RK713EYYdLo http://www.youtube.com/watch?v=6kW52Xj5KaA&feature=related

Solar energy for homes http://www.youtube.com/watch?v=Tj4KAWZFZOA&feature=related

http://www.youtube.com/watch?v=IELITZ2VSvk&feature=related Large scale PV power plants

http://www.youtube.com/watch?v=pXyJrFKwjrc&feature=related http://www.youtube.com/watch?v=L7PvUbQCLXY

Stirling motor solar power plant (not photovoltaic) http://www.youtube.com/watch?v=Z4joQSkQ1_M

http://www.youtube.com/watch?v=OTQ4cFn5sXs&feature=related New technologies

http://www.youtube.com/watch?v=SMnx5tFrDDc&feature=related http://www.youtube.com/watch?v=5NyhUQ3dmrw&feature=related

Solar power from space http://www.youtube.com/watch?v=V9YD9-_WTjk