5 - pv classes - characterization

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CHARACTERIZATIONCHARACTERIZATIONSolarSolar cellscells andand modulesmodules

CharacterizationCharacterizationSolar cell/modules characterization

Spectral responseIV curve

Other relevant testsDegradationReflectanceLifetime

Infrared mapping (luminescence)


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Spectral response


Spectral response (SR) is the short circuit current producedy e ce w en um na e y a g ven power

External quantum efficiency (EQE) is the probability of aincident photon contributing to one electron to the short circuitcurrentInternal quantum efficiency (IQE) is the probability of aabsorbed photon contributing to one electron to the shortcircuit current

opt

sc

P I

SR EQE hcq

SR

R

EQE IQE

1


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Spectral response

H. Mackel, Capturing the spectra of solar cells, PhD Thesis, Australian National University, 2004


Spectral response

E Q E

1

Back recombination

Reflectivity

=hc/E g

Front recombination


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Spectral response

Determination of diffusion length:

if -1


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IV curve


IV curve


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IV curve


IV curve: use callibration cell with same spectral response

or, if one knows spectral response of sample and reference cell andspectral irradiance of solar simulator, one may calculate themismatch error:

C.H. Seaman, Calibration of Solar Cells by the Reference CellMethod - The Spectral Mismatch Problem , Solar Energy, vol. 29, No.4, 1982, pp. 291-298


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IV curve

Class A Class B Class C

Spectral match 0.75 1.25% 0.6 1.4% 0.4 2.0%

IEC 904-9 : Requirements for solar simulators forcrystalline Si single-junction devices

Non-uniformity


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IV dark curve


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Reflectance

Sample

Lightsource

Monochromator Chopper

Lock-in Aluminium sample(high reflectivity)Zero background(low reflectivity)


Reflectance

S. Lust, et al, Mono and multicrystalline silicon solar cells based on macroporous silicon, Proc.of the 17 th EPVSEC, Munich 2001


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LifetimeMost common technique: Micro Wave P hoto Conductance Decay

Excess carriersgenerated by light

pulse

Monitoring variationof microwave

D.M. Macdonald, Recombination and trapping in multicrystalline silicon solar cells , PhD Thesis, Australian National University, 2001

reflectivity

Calculation of lifetime from decay

time constant


Lifetime

J. A. Silva, et al, Solar cells on silicon ribbons doped with sprayed boric acid as a doping source, Proc. 23 rd EPVSEC, Valencia 2008


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LifetimeCritical issue for lifetime measurements: surface passivationMay be achieved by many different approaches:

Growth deposition of a dielectric film or pn junction (e.g. a-Si)Corona discharge on SiO 2 filmImmersion in hydrofluoric acid ( HF)or alcoholic iodine solution

D. Pera, et al, Reliability of microwave photoconductivity lifetime measurements, Proceedings of the 23 rd EPVSEC, Valencia 2008


INFRARED IMAGING

IncludesElectroluminescence (EL)photoluminescence (PL) andlock-in thermography (LIT).

Allows measurement of Series or shunt resistanceJunction breakdownHot spotsLifetime

Kasemann et al, Progress in silicon solar cell characterization with infrared imaging methods, Proc. of the 23 rd EPVSEC,Valencia 2008


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CharacterizationCharacterizationINFRARED IMAGING SETUP .

Homogeneous irradiation of theentire solar cell is typically performedwith lasers in the wavelength rangefrom 790nm to 940nm. Differentcameras can be used to detectradiation in different wavelengthranges.

Spectral range of photon emissionfrom silicon solar cells, the underlying

mechanisms, and the detectors used.

Kasemann et al, Progress in silicon solar cell characterization with infrared imaging methods, Proc. of the 23 rd EPVSEC,Valencia 2008


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DEGRADATION

TESTS

Thermal Cycling(10.6)

Visual Inspection(10.1)

Damp Heat

(10.7)

Wet Insulation(10.5)

UV

(10.15)Humidity Freeze

(10.8)

Wet Insulation(10.5)

Load Test

(10.13)

ElectricalInsulation (10.4)

Dry Insulation(10.4)


Dry Insulation(10.4)



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Degradation: THERMAL CYCLING

Maximum celltemperature ( C)

TotalCycles

Applied Current

85 1000 Apply 1,25xISC when T>25 C.

Cycle speed is 10electrical/thermal

110 500

65 2000

After the Thermal Cycling, modules should be subjected to

To identify anddetermine any physicalchanges or defects in

module

Determine whether ornot the concentratorsystem is sufficiently

well insulated betweenthe active parts in the

power generating circuitand the frame or the

outside world


Electrical (or Dry) Insulation(10.4)


Degradation: DAMP HEAT

After the Damp heat, modules should be subjected to

Relative humidity should be controlled to 85 % 5% and the temperature to 85 C 2 C for 1000h.

The test should be continued for up an additional 60h to permit the insulation test to be performed.

To determine the ability of the modules or assemblies to withstand the effects of long term penetration of humidity.

To evaluate the insulation of theconcentrator system under wetoperating conditions and verify

that moisture from rain, fog, dewor melted snow does not enterthe active parts of the sample

Wet insulation(10.5)

Visual Inspection (10.1)

Electrical (or Dry) Insulation(10.4)

5 - pv classes - characterization

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