catalog_flir solar cell development

7/30/2019 Catalog_FLIR Solar Cell Development

1/5

Mill Ladle Reractory Monitoring

F L I R S o L u t I o n S e R I e S

The environmental and political benefts o renewable energy

sources are understood by anyone even mildly interested in

the uture o our planet. Solar cells are getting a lot o attention

because they are not only a clean source o renewable energy,

but also because their energy input is essentially ree. They use

photovoltaic (PV) technology to make a direct conversion o the

suns rays into electricity. According to John Boyd, a technology

analyst at Semiconductor Insights, a solar array 150 x 150 km

could, in principle, meet all o North Americas energy needs. [1]

Assuming adequate installation space, and a solution or power

grid load balancing, the main problem to be solved is

achieving grid parity, the point at which the cost o generating

PV power is competitive with that o generating power using

existing power plants.

Currently, the cost o generating PV power is approximately

$0.20/kWh globally, roughly twice the rate o coal-based alternatives.

Silicon solar cells are achieving conversion efciencies between

15% and 25%, while typical metallic thin flm cells have efcienciesin the 5% to 20% range, depending on materials used. R&D eorts are

aimed at increasing the efciency o both solar cell technologies

and reducing PV cell power generation costs to around $0.05/kWh.

The primary challenges in reducing the cost o PV power generation

exist in the production phase o the development cycle. Too many

deects in the semi-conducting material structure go undetected

beore solar cells are put into use. Identiying these deects

requires efcient, cost eective test and measurement methods or

characterizing a cells perormance and its electronic structure.

This paper is an overview of the methods in which FLIR InfraredCameras can be used to characterize solar cell performance.

Solar Cell Development



2/5


2

F L I R S o L u t I o n S e R


gure1.CircuitmodeloaPVcell.

Typical Cell Defects

PV cell is typically modeled as an ideal

iode in parallel with a photocurrent

ource, plus parasitic resistances such

s shunt resistance (RSH) and series

esistance (RS) (Figure 1).

Origins in Crystalline Structures

he conversion eciency o todays

licon solar cells is limited by ree carrier

ecombination, a processes by which

mobile electrons and electron holes are

bsorbed or lost, due to deects in the

ulk material. This is particularly true in

olar cells produced rom multicrystal-

ne silicon (mc-Si) waers, which have

gnicant concentrations o crystallo-

raphic non-uniormities such as disloca-

ons, grain boundaries, and impurities.

Lateral Non-uniformities

Non-uniormities in the current ow

cross a solar cell are an important

ssue in thin metallic lm PV develop-

ment. Since larger solar cell modules are

onstructed by connecting individual

V cells, a ew bad cells can afect the

erormance o the entire module. Oten,high RSH will be present as a result o

ny o the ollowing:

Improperhandlingduringprocessing

Diamondsawscribingatcellboundaries

Over-fringduringcellmetallization

Pooredgeisolationprocesses

Randomshuntsinherentinmost

productionprocesses

Series Resistance

The dominant sources o a solar cells Rs

are contact resistance, bus bar resistance,

screen-printed ngers, and lateral

conductions in the emitter. The relative

importance o each source depends on

the bias level and current ow in the cell.

For example, points near contact pads

typically have a much lower Rs than

those near the end o screen-printed

ngers. Process deects such as breaks in

ngers, or poorly printed areas, add to

the variation in Rs.

Measurement Methodologies

All three types o deects mentioned

above can have a signicant efect on

a PV cells charge carrier characteristics

and conversion eciency. Some o the

parameters most commonly measured

include resistivity (used to screen silicon

waer materials) and other electronic

characteristics o PV cells, such as I-V

curves, charge carrier/current density,

ree charge recombination lietime, bulk

material lietime, and efective lietime.

Many diferent techniques are available

or measuring these parameters and

detecting deects. They vary greatly in

terms o complexity, equipment cost,

and the time required or completing a

typical set o measurements. Depending

on the product development stage, these

techniques can be employed in an R&D lab

or on a production line. In the latter case,

testing may be used or troubleshooting

or optimization o production processes,

or nal testing o completed cells.

In general, PV cell tests are based on three

broad areas o technology: spectroscopy,

electrical (contact) measurements, and

inrared (IR) imaging. Frequently, multiple

techniques are employed to collect a wide

range o parameters, particularly in R&D labs.

Electrical Testing

For silicon waers, some o the more

commonly used R&D methodologies

include capacitance-voltage (C-V)

measurements and resistivity proling.

Waer resistivity can be checked by

classical our-point (Kelvin) probe

measurements typically, using the our-

point collinear probe method or the van

der Pauw method. For accurate resistivity

measurements, waer thickness must be

determined, which requires additional

optical techniques or capacitive gauging.

The techniques that make electrical

contact with a waer may require special

sample preparation steps. As you might

suspect, they are oten time consuming,

which places practical limits on the

number measurements and samples

that can be processed within available

timerames.

In production and process development

testing, typical electrical parameters o

interest include short circuit current (ISC),

open circuit voltage (VOC), Fill Factor (FF),

Ideality Factor (), series resistance (RS)

at VOC, shunt resistance (RSH) at 0V, and

reverse voltage breakdown. FF and are

usually derived rom I-V measurements. A

recently developed Sun-VOC technique

allows reconstruction o the I-V curve in a

single light ash without the inuence o

(RS). Dark I-V measurements can also reveal

lumped series & shunt resistance problems.

Since a solar cells eciency is largelya unction o its short circuit current,

open-circuit voltage, and ll actor, these

parameters tend to be the ocus o much

testing, even in R&D labs. VOC and FF can

be characterized by the shape o the

orward biased dark I-V curve. Frequently,

distribution o orward current density

over the entire cell is inhomogeneous.

I current density through a given

region is higher than the cell average,

this is indicative o a shunt. Thereore,

characterizing shunts under orward-bias

conditions is important in the eforts to

increase eciency.

Shunts associated with ront side metallization

can be detected using the Parallel Resistance

Analysis by Mapping o Potential method

(PRAMP). However, PRAMP cannot detect

shunts below the metallization. Another

potential drawback arises because a

tungsten probe is used to penetrate

the cells antireection coating, which

scratches the surace to a certain degree.

Parasitic series resistance is important as

it is a major contributor to a PV cells FF

losses and ideality actor, . Typically, RS

is determined rom a set o illuminated

and dark I-V measurements. While these

use straightorward methods, collecting a

complete set can be a bit time consuming.

Conventional IR Imaging Methods

Standard thermographic imaging o solar

cells as a means o detecting deects has

been used or over a decade. In most cases,

it allows ast detection o the major shunts

by the application o a reverse bias voltage,

or by just observing the temperature o

the cell under typical operation. However,

the sensitivity and thermal resolution

o standard thermography is limited by

an IR camera systems inherent detector

sensitivity, or noise equivalent temperature

diference (NETD). The NETD or cooled

cameras with indium antimonide (InSb)

detectors is ~20mK, and ~80mK or an

uncooled microbolometer) (Figure 2).

This image in Figure 2 was captured using

an uncooled microbolometer camera

with a spatial resolution o 320 x 240

pixels. The triangular shapes on the let

and right o the cell are alligator clips

used to apply bias voltage; the circular

area is a reection o the camera lens.

The bright orange spots and less bright

orange regions in the upper right hal

o the image indicate increased thermal

activity due to shunts. Only severely

shunted areas become visible as bright

and localized spots. The darker orange

regions are a result o weaker shunt

deects. Locating the origins o theseweaker shunts is extremely dicult, i not

impossible due to the thermal difusion

(spreading o thermal energy over time)

as well as the weak thermal radiation o

the deect itsel.

Still, these cameras provide the ability to

quickly spot major deects that would not

show up in visible light images. Visible

light images, however, still provide useul

reerence points alongside IR images (Fig. 3).

Today, cameras are available that combine

both IR and visual imaging, making ast

steady-state testing o solar cells very

convenient (Figure 4).

A slightly more complex method

conventional IR imaging to dete

is moving a heat lamp and came

attached to a xture across the s

o the cell, or more commonly, a

panel. For example, a major aero

manuacturer ound that their cr

detection rate went up and insp

times went down when they had

operator view the digital data im

an InSb camera that was mounte

degrees to a large solar panel illu

with a heat lamp at the opposite

degree angle. This technique use

motion control system that mov

lamp and camera across the larg

panel. The operator has a system

deects as they show up on the d

Any cracks in the panel cause the

energy to difuse through the m

diferent rates and are much mo

in the thermal image than they a

using eyes alone.

To improve crack detection in PV

requires a more sophisticated ap

The drawback o using a slowh

excitation source is that the resu

thermal difusivity will be signic

negatively afecting the spatial r

and denition o the crack.

Now there are commercial, of-th

systems or solar panel inspectio

such as the SolarChecksystem

MoviTHERM, Irvine, CA, USA (ww

movitherm.com), that use either

ash or a modulated laser excitat


Figure2. IRimage o60x60mmsilicon solarcell showingshuntdeects(orangeareas)understeady statereversebias conditions.

Figure3.Solarcell testingusingan uncooledmicrobolometerhandheldcamera.

Figure4.FLIRSC660camerawith bothvisiblelightimagingusingan uncooledmicrobolometerdetec


3/5



4



Solar Cell Development Solar Cell Development

rack detection. The SolarCheck system

ynchronizes the excitation source to

he camera and perorms a Lock-in

hermography measurement, which

ollects a sequence o hundreds o

mages. This has the distinct advantage

eliminating problems arising rom

eections o other heat sources, such as

uman body radiation, overhead lights,

tc. An additional benet is the signicant

ncrease in sensitivity o the system due

o the Lock-inprinciple. This brings the

etection threshold o the system down

elow the noise oor o the camera by a

actor o 100 to 1000.

igure 5 illustrates the benets o this

echnique. The measurement was

erormed with a SolarChecksystem

sing a single-sided (reective) setup.

he laser and the camera were located on

he same side o the PV cell (backside).

Electroluminescence (EL)& Photoluminescence (PL)Techniques

EL and PL are techniques used to

generate spatially resolved images o

solar cells that reveal localized shunts,

series resistance, and areas o charge

carrier recombination. EL applies a

orward voltage and current to cause

localized irradiance due to carrier

recombination (Figure 6). PL uses light

irradiation or the same purpose.

Figure 6 illustrates an EL test setup in

which the current ow causes the PV

cell to emit light in the near inrared

(NIR) range o the spectrum. This

measurement setup is able to examine

the uniormity o the solar cell with

respect to its ability to convert photons

into electrons. This is shown in Figure 7.

Since EL and PL techniques only work

in the NIR region, both types o system

require a camera with a cooled NIR

detector. (Uncooled microbolometer

detectors are long wave IR instruments

and thereore not suitable here.) A

typical indium gallium arsenide (InGaAs)

IR camera used or EL and PL deect

studies is the FLIR SC6000 (Figure 8).

Care must be taken during EL testing,

however, to avoid applying a destructive

amount o current to the solar cells. In

cases where the solar cells may be more

vulnerable to damage rom EL test

currents, lock-in thermography presents

an alternative method.

Lock-in Thermography

Rened thermal methods are needed to

detect a wider variety o shunt conditions,

particularly those below a solar cells

metallization layer. Since around the

year 2000, researchers have used the

technique o lock-in thermography

(LIT) to overcome the limitations o

conventional thermographic imaging.

By stimulating a PV cell with pulsed

light, heat, or electrical signals, a lock-

in amplier tuned to the excitation

requency o the stimulus allows

the system to detect subtle thermal

responses beyond the noise oor

limitations o the camera. This technique

is capable o detecting temperature

diferences with microKelvin resolution,

ar exceeding the 20mK resolution o

modern InSb cameras.

Historically, these test systems were

custom in-house developments and

no commercial-of-the-shel solution

existed. Now MoviTHERM supplies a

system that integrates FLIR IR cameras

with sotware modules rom a German

company, Automation Technology (www.

automationtechnolody.de) or a complete,

commercially available LIT test solution

called SolarCheck.

Figure 9 is an image o shunt deects

identied with this type o LIT system. The

illuminated LIT technique allows mapping

o orward current density distribution,

and can also reveal series resistance and

sites where there is heightened carrier

recombination.

Compare Figure 9 to Figure 2. Note

that the image resolution in Figure 9 is

better (i.e., not difused and blurry), withlocalized shunt deects more sharply

dened by the orange areas. With LIT,

the reection o the camera lens and

outlines o the alligator clips no longer

obscure large portions o the image, as

they do in Figure 2. LIT also requires

signicantly less energy input to the

solar cell compared to conventional

thermography. One reason is because

measurement sensitivity is about 1000X

better around 0.02mK. These sharp LIT

images provide additional inormation,

such as non-uniorm heating o the cell,

as revealed by lighter and darker blue areas.

Lock-in Thermographyfor Shunt Detection

Figure 10 shows the results o LIT testing

or shunt deects on cells that were

electrically excited with a sine wave.

It illustrates the efect o modulation

requency on the thermal difusion, and in

turn on the resulting spatial resolution o

the phase image.

Figure 11 is another LIT test result. In this

example a comparison is presented or

10Hz and 200Hz excitation requencies.

At 10Hz, many o the deects go

undetected. Only the more seve

shunted areas show up aintly a

excitation requency. On the rig

with the 200Hz excitation, the s

deects are much more pronoun

exhibit an improved spatial reso

Some experimentation may be

to nd the best stimulation req

electrically excited LIT measure

When modulated light is used a

PV cell stimulus, LIT does not re

electrical contact with the DUT

the measurements (Figure 12). H

i VOC measurements are desire

option does require electrical p

shown in Figure 6. Regardless o

o stimulus used, the power diss

by PV cell deects is amplitude-

modulated, and thereore the re

thermal image is one o periodi

temperature modulation.

gure5.Top:a solarpanelbeingexposedtoashortlaserulse,shownas abright whitehorizontallineat t= 0mson theystallinePVcell.Bottom:thesamePVcellatt= 200msaterlaserposureandheatpropagation.The lighterareawith theirregularoundarylineclearlyreveals acrack.

Figure6.Measurementsetup orEmissionAnalysisusingMoviTHERMsIR-NDTsystemSolarCheck.The PVcell(orsolarpanel) isbeing electricallystimulated(electroluminescencetechnique).

Figure7. Imageosolar celldeectsidentiedthroughEmissionAnalysis.This imageresultsrom thetestsetup inFigure6. Thedarkareasnearthebottomotwocellsintheupperletrepresentdeects.

Figure8.TheFLIRSC6000IR camerawitha cooledInGaAsdetectorcanbe usedto mapsolar celldeectsusingEL orPL techniques.

Figure9. ImageothesamesolarcellinFigure2,nowshowingshuntdeectsmoreclearly (orangeareas)whenmappedwith anLITtechnique,usingthe MoviTHERMsSolarChecksystem.

Figure10.Phaseimageso shuntdeectsromlock-inmeasurementsperormedwith theSolarChecksystemat 10Hz(top)and200Hz (bottom)sinewavestimulation.

Figure11.LITphaseimages intendedtoshow shuthatinthe topview (10Hzstimulation)manydeecinvisible.Theyshowup clearlyinthe bottomviewawith200Hzstimulation.


4/5



6



Solar Cell Development Solar Cell Development

However, the system shown in Figure

2 uses a sotware-based lock-in

mplier. This employs a technique

alled phase sensitive detection to

ngle out the signal at a specic test

requency. Because the lock-in ampliernly measures AC signals at or near the

est requency, noise signals at other

requencies are largely ignored. Typically,

test requency o only a ew Hz is used

o get below the requency o most

oise sources, and thereby optimize

ystem sensitivity. This allows the LIT

ystem to detect thermal changes well

elow the noise oor o the camera.

hus, FLIR InSb and InGaAs cameras can

e used or LIT, and image resolution is

mited primarily by the pixel resolution

the cameras ocal plane array detector

nd selected optics. The pixel size o the

LIR SC6000 is 25m and a wide range

optics is available, rom a wide eld

view down to microscopes capable o

um/pixel spatial resolution.

he amplied signals rom the DUT

s multiplied by both a sine and a

osine wave with the same requencynd phase as the stimulus and then

ut through a low pass lter. This

multiplication and ltering can be

one with analog circuits, but is more

ommonly perormed digitally within

he lock-in amplier on the DUTs

igitized response signal. The outputs o

he low pass lters are the real (in phase)

nd imaginary (out o phase) content o

he PV cell response signal.

As opposed to the amplitude

image obtained with conventional

thermography, LIT produces a phase

image on a pixel by pixel basis rom the

cameras temporal (time varying) data.

This means that emissivity, reection,

and absolute temperature measurement

no longer afect the results obtained.

Images and cell parameters are

calculated by the system sotware

running on a PC. With appropriate

sotware, the processed signal rom

the IR cameras detector can be used

to make quantitative measurementso I-V characteristics associated with a

localized shunt, calculate the reduction

in cell eciency due to shunts, and map

saturation current density and ideality

actor over the entire cell.

Quantifying ChargeCarrier Behavior

In addition to spatial identication

o deects, most researchers want to

characterize charge carrier behavior in PV

waers and cells. A number o techniques

have been developed or this purpose.

For example, the electronic properties

o silicon waers can be characterized

using surace photovoltage (SPV),

microwave photoconductivity decay

(W-PCD), charge density imaging (CDI)

techniques, and quasi-steady-state

photoconductance (QSSPC). Some o

these techniques can also be used to

monitor PV cell production. For example,metallization processes inuence the

efective lietime o charge carriers, which

becomes an important parameter to monitor.

However, many o the techniques

mentioned require special waer

preparation and are rather time

consuming. CDI is one exception. It can

be implemented with LIT, and used to

map saturation current density, and other

parameters, over an entire PV cell.

Flash CDI is based on ree-carrier

absorption o photo-generated excess

carriers, and thus allows the imaging o

charge carrier lietime properties. With

lock-in processing o the signal, much

shorter lietimes can be measured.

In this technique a black body source

emits IR, which is transmitted through

the DUT and measured by an IR camera.

In addition, excess ree-carriers are

generated by the chopped light rom a

semiconductor laser, which modulates

IR absorption and transmission. Carrier

generation is controlled by adjusting thelaser intensity to approximately a 1-sun

level. The laser light is chopped at a low

Hz rate, to ensure steady-state conditions

and help reduce lock-in measurement

noise. With proper calibration, efective

lietime is obtained, and test time can be

on the order o seconds. An entire CDI

waer map can be created in a minute or so

at a resolution better than that obtained

with many other techniques, some o

which are an order o magnitude slower.

Actual CDI test times depend on

the length o the efective lietimes

being measured. A larger number o

image rames need to be processed

or lower lietimes, which takes longer.

Nevertheless, higher injection levels can

help shorten test time.

A CDI version o an LIT system is shown

as a block diagram in Figure 13. The

hotplate provides black body radiation,

while the pulsed laser light generates

minority carriers in the PV cell. For each

o the IR camera detector pixels, the

signal output is proportional to image

intensity. The resulting signal is a step

unction, with amplitude levels that

can be designated as DON and DOFF.

The diference, D, is proportional to

absorbed light intensity, and thereore

represents the ree carrier concentration

at that pixel point in the cameras eld o

view. The complete set o pixel outputsproduces an image o the carrier density

distribution (or efective carrier lietime),

with a contrast that is proportional to D

(Figure 14).

As implied above, the intensity o each

pixel, IA, is equal to D. By assuming that

carrier lietime is homogeneous over

the entire sample width, and applying a

sinusoidal correlation procedure, it can

be shown that:

D = km W,

where kis the sinusoidal correlation

actor, m = excess minority carrier

concentration, and Wis the sample

width.

The correlation procedure sets the

cameras rame rate based on the lock-in

requency. This allows measurements

under a steady-state condition or the

carrier density during every hal period

o the stimulus signal. The steady-state

measurements o m values can be used

to calculate the efective carrier lietime

according to:

ef= mW/ G = IA / -kG,

where G is the local generation rate or

the sample area.

Since a PV cell can be modeled as

an ideal diode in parallel with a

photocurrent source, LIT can be

used to thermally measure local I-Vcharacteristics that reveal non-ideal

behavior, i.e., parasitic series and shunt

resistance. Non-ideal diode properties

o the PV cell are also expressed in the

Ideality Factor,

= V/ln(I).

By accounting or source resistance, R S,

and shunt resistance, RSH, a relationship

between and PV cell voltage can be

established, which leads to a better

understanding o charge carrier

transport mechanisms.

LIT can be combined with illuminated

and dark I-V measurements to derive

other PV cell parameters. For example,

the Fill Factor is also lower than ideal due

to RS and RSH. It can be expressed as:

FF = Impp Vmpp / ISC VOC,

where mpp is the maximum power point.

Conclusions

A major advantage o LIT compared

to many other test methods is the

short time required to complete a set

o measurements without elaborate

sample preparation. Once an LIT system

is congured, signicant amounts

o data can be acquired in seconds,

compared to minutes or hours with

other methodologies. This make

a good candidate or process rela

testing, as well as or use in the R

lab. The MoviTherm SolarCheck

system, with appropriate stimula

sources and accessories, can be u

or all common IR solar cell testin

methods including crack detect

electroluminescence, photolum

lock-in thermography, and charg

imaging.

Acknowledgements

The thermographic measuremecapabilities o the LIT systems m

in this paper are based on IR cam

supplied by FLIR Systems, Inc. Ma

the parameter extractions are pr

in Lock-In sotware IrNDTsupp

by Automation Technology Gmb

Germany (www.autmationtechn

Complete, integrated LIT system

the SolarChecksystem can be o

rom MoviTHERM, Irvine, CA, USA

movitherm.com). Engineers and

o these companies have contrib

or perormed peer reviews o thi

FLIR Systems

Thermography Division25 Esquire Road

N. Billerica, MA 01862

800-464-6372 (800-GO-INFRA)

MoviTHERM

15540 Rockeld Blvd., Suite C100Irvine, CA 92618, USA

949-699-6600 Phone949-699-6601 Fax

www.movitherm.com

Contact: Markus Tarin, President & CEO, m

movitherm.com

Automation Technology GmbH

Hermann-Bssow-Strae 6-8

23843 Bad Oldesloe

Germany

Phone: +49- 04531-88011-0

Fax: +49-(0)4531-88011-20www.automationtechnology.de

gure12.Non-contactLITtestcongurationusingmodulatedghtasthePVcellstimulus.OptionalVOCmeasurementsdoquireelectricalprobingo thecell.

Figure13.Blockdiagramo aCarrierDensity ImagingsystemusingLITbased ontheSolarChecksystem.

Figure14.Spatialmapo PVcell areashowingefectivecarrierlietimes(ef)in microseconds.


5/5




FLIR invented the inrared camera industry as we now know it. We brought the rst commercial IR camera to market in the 1960s

and have piled up more industry rsts in thermal imaging than anyone. Today we are the only global company totally dedicated to

nding and xing thermal problems through IR imaging systems. Our companys mission is to provide the most innovative systems

available, with the highest possible quality, and show thermography practitioners how to get the most out o them. Our goals,

now and in the uture, are to provide greater insight into all types o thermal phenomena, and help our customers save money by

applying this knowledge. This is supported by the most comprehensive and respected training courses in the industry.

FLIRs smart IR cameras are used in basic research, non-destructive testing, product development, actory automation, equipment

and building maintenance, asset protection, medical diagnostics, public saety, national deense, and a host o other applications. No

other company ofers the breadth o thermal imaging/temperature monitoring products supplied by FLIR, and none is as dedicated

to technical excellence as our 350+ engineers. Within the past three years alone, FLIR has spent more than $230 million on R&D. Our

customers are the primary beneciaries o this investment, enjoying an ROI that amounts to millions o dollars a year in direct savings

rom operating eciencies and loss avoidance. As a result o this leadership, FLIR is the most trusted name in the industry.

WE KNOW INFRARED. LIKE NOBODY ELSE.

REFERENCES

[1] J. Boyd, Under the Hood: The next gold rush - solar power, TechInsights Div. o United

Business Media (March 10, 2008), www.techonline.com/product/underthehood/206904953.

[2] S. Riepe et al, Carrier Density and Lietime Imaging o Silicon Waers by Inrared Lock-in

Thermography, 17th EU-PVSEC Munich (2001), paper VC1.51..

[3] J. Schmidt, et al, Advances in Contactless Silicon Deect and Impurity Diagnostics Based on

Lietime Spectroscopy and Inrared Imaging, Advances in OptoElectronics. Vol. 2007, Article ID

92842, Hindawi Publishing Corp.

[4] C. Balli et al, Ecient Characterization Techniques For Industrial Solar Cells and Solar Cell

Materials, Proc. 12th Workshop on Crystalline Silicon Solar Cell Materials and Processes, NREL,

Breckenridge, CO, USA (2002), pp. 136-146.

[5] M. Tajima et al, Characterization o Multicrystalline Silicon by Photoluminescence

Spectroscopy, Mapping and Imaging, Institute o Space and Astronautical Science/Japan

Aerospace Exploration Agency (2006), email [email protected].

[6] A. Hauser et al, Comparison o Diferent Techniques or Edge Isolation, 17th EU-PVSEC

Munich (2001), email [email protected].

[7] M. Kasemann et al, Comparison o Luminescence Imaging and Illuminated Lock-inThermography on Silicon Solar Cells, Applied Physics Letters 89, 224102 (2006).

[8] D. Shvydka et al, Lock-in Thermography and Non-uniormity Modeling o Thin-Film CdTe Solar

Cells, Applied Physics Letters, Vol. 84, No. 5, (Feb. 2004).

[9] J. Rakotoniaina et al, Quantitative Analysis o the Inuence o Shunts in Solar Cells by Means

o Lock-in Thermography, 3rd World Conerence on Photovoltaic Energy Conversion (2003),

Osaka, Japan, re. 4P-A8-62.

[10] O. Breitenstein et al, Shunt Detection in Solar Cells with the CoreScanner and Lock-in

Thermography: A Comparison, Proc. 11th Workshop on Crystalline Silicon Solar Cell Materials

and Processes, NREL, Golden, CO, USA (2001).

[11] O. Breitenstein et al, Quantitative Evaluation o Shunts in Solar Cells by Lock-In

Thermography, Progress in Photovoltaics Research and Applications (2003), 11:515526.

[12] I. Konovalov et al, Activation Energy o Local Currents in Solar Cells Measured by Thermal

Methods, Progress in Photovoltaics Research and Applications(1998), 6:151-161.

For more information:

Call: 1 800 464 6372

Web: goinrared.com

catalog_flir solar cell development

Documents