13 edler isc konstanz

Flasher setup for bifacial measurements

Alexander EDLER, Michel SCHLEMMER, Joachim RANZMEYER, Rudolf HARNEY

Outline

MotivationIntroduction of the add-on setupCharacterization of the setupCapacitance effects Bifacial measurements

Alexander Edler, bifiPV workshop, Konstanz, April 23rd 2012

Bifacial measurementsSummary

- 2 -

Motivation

− Measure cell properties under actual operating conditions (using albedo) in a controlled environment

− Additional effects in bifacial measurement over std. measurement?

− New module sorting methods


− New module sorting methods required?

− Appropriate measurement procedure to quantify the energy yield for bifacial operation?

− Customize cell process for bifacial module operation?

- 3 -

Bifacial cell tester

− Single light source at 1,7m distance

− 2 perpendicular mirrors− Reference cell in measurement

plane− Conventional flasher contacting

frame


frame

- 4 -

Ezquer et. al., Proceedings of 25th EUPVSEC Valencia 2010

− Aluminium coated mirrors @ 45°AOI

− Rack installed in Berger flasher system

Grid

PT100 temperature sensor instead of IR sensor

Cells contacted in standard frame, which can be removed to change cell

Bifacial cell tester

Alexander Edler, bifiPV workshop, Konstanz, April 23rd 2012 - 5 -

Reference cell in top view

std. meas. (10x) with covered rearside E1-C123

ISC [A] 9,297

VOC [V]0,645

FF [%]75,6

eta [%]18,81

First meas. (10x) in bifacial rackwith covered rearside E1-C123 9,262 0,645 75,8 18,79

Spectrum characterization

6

8

10

12

70

80

90

100

110Irradiance [W/m

²nm]

Comparison Spectra & %R Mirror

%R Mirror @ AOI=45°

E without Mirror [W/m²]


0

2

4

6

300 500 700 900 1100 1300 1500 1700

30

40

50

60

70

Wavelength [nm]

Irradiance [W/m

²nm]

E without Mirror [W/m²]

E wih Mirror [W/m²]

- 6 -

Reflected light within Class A specification for AM1.5G

Intensity filter steps

100110

400383

80 =1000*0,8*0,2*0,582

expectedmeasured

Intensity without any filter [W/m²]measured1000


20% covered area 50% covered area 80% covered area

160185

800803

500476

200230

Partial shading is achieved using intensity filters at 30cm distance from the cell

Illumination homogeneity

20

10

00 10 20 30 40 50

current

[A/cm²]

X Axis [cm]

Y Axis [cm]

0,1200

0,1247

0,1293

0,1340

0,1387

0,1433


40

30Y Axis [cm]

0,1433

0,1480

0,15270,1550

Specification of flasher setup states homogeneity of intensity <2%» Larger area increases the intensity variation » 7% (min-max) variation over cell area -> Class B according to

measurement standards

Summary bifacial setup

+ Easy to use+ Simple construction+ Add-on for individual existing

system+ Constant temperature

measurement+ 1 reference cell to correct for

- Illumination homogeneity Class B

- Currently limited to 16A- Discrete illumination levels


+ 1 reference cell to correct for intensity fluctuations

+ Inline compatibility

- 9 -

• Illumination level covers relevant range(1-1,5 suns)

• Option to measure 1-cell modules

• Direct rearside illumination instead of diffuse light

Problems with fast IV-Sweeps

− Fast voltage sweeps induce IV curve distortion

− Significant for all high-efficiency, high resistivity and especially for n-type based cells

− Depending on measurement direction and illumination intensity

6

8

10

[A]

FF=75,3%

FF=80,1%


intensity− Asymmetric effect− Not limited to bifacial

measurements− ISC and VOC evaluation not

affected

- 10 -

0

2

4

0,3 0,4 0,5 0,6 0,7

I [A

]

U [V]

OC-SC

SC-OC

Diffusion capacitance explained

1E+12

1E+13

1E+14

1E+15

MC

D d

ensi

ty [c

m-³

]

U=0VU=0,3VU=0,5V


− Diffusion capacitance consists of bulk minority charges.− Applying forward bias changes equilibrium concentration by orders of

magnitude! » large amounts of charge − Allocation/ generation of these charges in “ms” range requires a

charging current, which is subtracted from external current» Measurement error

- 11 -

1E+110 50 100 150

distance from junction [µm]

U=0,5VU=0,6V

8,0

8,5

4,4

MPP scan approach

− 1st measurement to collectISC &VOC values

− 2nd measurement to scan narrow MPP interval only

» We artificially extend the measurement time available


0,44 0,55

7,5

8,0

0,48 0,50 0,52 0,54 0,563,8

4,0

4,2

I [A

]

U[V]

MPP scan SC-OC MPP scan OC-SC SC-OC full IV scan OC-SC full IV scan

P [W

]

U [V]

measurement time available for each data point

» Self-validating method as scans in both directions match

» Works for all cell types available at ISC

- 12 -

Bifacial measurements

FF [%] ISC [A]

77

77,5

78

78,5

12

13

14

15

textured rear1

textured rear2

flat rear (2Ohm cm)

flat rear (5Ohm cm)


Cell types: textured rearside vs. flat rearsidelow vs. high resistivity

- 13 -

Effective Intensity [suns]

75

75,5

76

76,5

77

1 1,1 1,2 1,3 1,4 1,5

8

9

10

11

12

1 1,1 1,2 1,3 1,4 1,5

flat rear (5Ohm cm)

Bifacial Bifacial


VOC [mV]

PMPP[W]

644

646

648

650

652

654

textured rear14

4,5

5

5,5

6

6,5

7

1 1,1 1,2 1,3 1,4 1,5

Bifacial


636

638

640

642

1 1,1 1,2 1,3 1,4 1,5

textured rear1

textured rear2

flat rear (2Ohm cm)

flat rear (5Ohm cm)

1 1,1 1,2 1,3 1,4 1,5

17

17,5

18

18,5

19

19,5

20

1 1,1 1,2 1,3 1,4 1,5

η [%]

Effective intensity [suns]

Bifacial

Bifacial


8

10

12

14

16

18f(0-1),r(0)

f(0), r(0-1)

f(1), r(0-0,5)

f(0-1), r(1)

sum f(0),r(0-1)+f(1)

74

75

76

77

78FF [%] IMPP [A]


0

2

4

6

8

0 0,5 1 1,5 2

71

72

73

74

0 0,2 0,4 0,6 0,8 1 1,2 1,4

Effective intensity [suns]

BifacialSingle side BifacialSingle side

Measurements show linearity in ISC and IMPP

» Both could be used for cell sorting

Summary

− We have installed a setup for bifacial measurements in our Berger flasher

− IEC flasher measurement criteria could be fulfilled, with the exception of spacial homogeneity required for Class A

− A solution for the accurate testing of high capacitance cells was found− Initial measurements have demonstrated suitability for bifacial

investigations


− No obvious reason for inline bifacial sorting found

We measure your cell!

- 16 -

Summary

− We have installed a setup for bifacial measurements in our Berger flasher

− IEC flasher measurement criteria could be fulfilled, with the exception of spacial homogeneity required for Class A

− A solution for the accurate testing of high capacitance cells was found− Initial measurements have demonstrated suitability for bifacial

investigations


− No obvious reason for inline bifacial sorting found

We measure your cell!

- 17 -

Thank you for your attention!

13 edler isc konstanz

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