Long-Term Performance Data and 

Analysis of CIS/CIGS Modules 

Deployed Outdoors

J. A. del Cueto, B. Kroposki, S. Rummel, Allan Anderberg. 

National Renewable Energy Laboratory 

Golden, CO USA

Sunday, August 10, 2008

NREL/PR-520-43838

Presented at the Society of Photo Optical Engineers’ (SPIE) Optics+Photonics conference

held August 10-14, 2008 in San Diego, California.
Outline

 Introduction

 Rationale for thin-film CIS PV modules: cost - high efficiency

 Identify loss modes and/or sources in CIS/CIGS modules

 Module deployment &Tests at NREL OTF

 two manufacturers, types ‘A’ & ‘B’, on 3 separate testbeds

 Analyses 2 types of data, 

 STC & dark I-V standard diode devices

 Real-time field data analysis

 Conclusions

 FF degradation is predominant loss mode

Type ‘A’ can show very low rate to moderate loss rates

Series-resistance increases symptomatic of A modules

Type ‘B’ can show very low loss rate to nominal loss rate

Shunt increases & other subtle changes or failure mechanisms

 Transient behavior observed especially after dark storage
Introduction

 Thin-film PV technologies (CIGS, CdTe, a-Si/nc-Si) are expected 

to achieve and compete for lowest cost per watt vs. bulk 

technologies (c-Si, poly-c-Si) largely because of economy in and 

costs of semiconductor materials usage;

 Copper indium diselenide (CIS) and/or gallium-alloyed CIGS 

photovoltaic (PV) modules achieve some of highest PV conversion 

efficiency of the thin-films:

 Current state-of-the-art CIGS efficiency at Standard Test 

Conditions (STC):

 cells attain 19.9%

 modules ( ~ 0.4 - 0.5 m2) attain ~12% 

 CIGS PV module stability issues need addressing

 issues under damp/dry heat exposure

 high-voltage bias applications for electrical power
Introduction: performance & reliability loss modes

 FF losses:

Series resistance (Rse) increases: 

degradation of top TCO (ZnO) resistivity 

CdS/CIS interface

Shunt conductance (Gsh) 

Diode qualities (A, J0) & recombination

Voc losses:

electronic carrier effects in CIS,

band offsets,CdS/CIS interface 

Isc loss modes not obvious, but possibilities: 

transparency of top TCO, EVA

Rse increases are very large
Experimental Tests at OTF

 Two manufacturers of modules ‘A’ & ‘B’

 glass/Mo/CIGS/CdS/ZnO/glass laminates

 type A deployed beginning in 1988, 5 vintages

 type B deployment began 2002

 Other CIS manufacturers also at OTF but not reported

 Study CIS/CIGS modules deployed on 3 testbeds:

 Single units, free-standing, long-term exposure, loaded at 

Pmax (STC) with fixed resistor, 9 total

 High Voltage Stress Testbed (HVST2) Array

 consists of 2, bipolar strings, nominally ± 300 VDC open circuit

12 type ‘A’ CIGS modules per string, 24 total

I-V traces monitored & loaded continuously with DAS

 Performance & Energy Ratings Testbed (PERT)

I-V traces monitored & loaded continuously with DAS

A module 1997, B module 2002
PERT & HVST2 Array Module Deployment

 Performance & Energy Ratings Testbed 

(PERT)

 Open-air steel frame mounts, face due 

south, tilted at 40° latitude with 

respect to horizontal

 Meteorologic resources (Irr, module 

& air temps., etc)

 Array: High-voltage stress test (HVST2)

 Same sensors as PERT, plus RH

 Elevated, frames electrically floated 

to measure HV leakage currents

PERT: viewed looking west

HVST2 array: viewed looking east
Long-term free-standing single module deployment

 loaded with fixed resistor, 

 9 modules total

 Also tilted at latitude angle, 

facing south

 open-air steel rack mounts

Long-term exposure rack seen looking east

1988 A module installed 20 years
Data Analysis: STC or dark at 25°C

 Single I-V curves at STC or dark at 25°C

STC data: SPIRE, LACSS or SOMS

 LACSS & SOMS use P/S to drive I-V traces

Module data normalized to unit area cell (J-V):

 dividing voltage by series cell count (Ncell)

 dividing current by area per cell (Acell = AperArea / Ncell)

Standard PV device diode circuit model with 

parasitic series resistance (Rse) and shunt conductance (Gsh)

 determined Rse, Gsh (dark) allows raw data to be corrected 

and then to derive A, J0 
Diode Analysis: Rse, diode Q, Gsh, J0

 Diode Eq.

 Derive 3-pnt slopes dV/dJ 

(Rse) or dJ/dV (Gsh) & 

correct data for series & 

shunt

dV/dJ vs. 1/J or 1/(J+Jlight)

Intercept = Rse, 

slope = A (kBT/q)

Gsh: from dJ/dV minimum 

near 0 V

V –> Vcor = V -RseJ, 

J –> Jcor = J - GV

Ln(Jcor)-Vcor => J0, 

Also A => slope V vs. LnJ

J = J0 * [ eq(V-RseJ)/AkT - 1 ] + GSHV - JL dV/dJ (Ohm-cm2) 0

5

10

15

20

25

1/J (cm2/A)

0 100 200 300 400 500

V (volts)

Ln[J] (mA/cm2)

0.0 0.1 0.2 0.3 0.4 0.5 0.6

Measured

Corrected

10-6

10+2

10-4

10-2

100
Data Analysis: PERT & HVST2

 Real-time outdoor data measured in situ with 

programmable electronic loads & DAS

I-V power parameters (Voc, FF, etc.) data condensed

segregated into narrow irradiance bands (±25 W/m2) for all 

illumination intensities, 

Linear regression vs. module temperature (Tmod) each bin: 

Parameter Y: Y(Tmod) = Y0 + dY/dTmod * Tmod

select bands analyzed 250, 500, 1000 W/m2, vs. time

averaged to cover 3 select windows for ±75 W/m2 span

 cover most of energy-producing field conditions

Data partitioned to 3-month intervals

Power parameters, Rseries, diode Q factor derived for each

Changes in power parameters vs. time calculate
Single module data at STC (SPIRE or LACSS)

 Manufacturers A & B: 

 A: (5 vintages) 1988, 1990, 1992, 

1994, 1998; 

 B: 2002

 A module initial efficiency

 from 8% (1988) to ~ 11-12% (1998)

 Low loss rates earlier 1%/yr or less

 stability became issue when initial 

efficiency exceeded ~ 9%:

 FF losses account for most decline

 Voc increases in initial years, partly 

offset FF losses, but subsequently 

can degrade

 B module initial efficiency ~11% 

 slight decline mostly in FF, partly 

offset by Voc increase during first 

years 1/88 1/90 1/92 1/94 1/96 1/98 1/00 1/02 1/04 1/06 1/08 Efficiency (%) FF (%) Voc (V) B Modules A Modules Voc (V)

50

51

52

53

22

23

24

25

26

27

Taken out of service

45

50

55

60

65

70

5

6

7

8

9

10

11

12

1988 A

1990 A

1992 A

1994 A

1997 A

1998 A

2002 B

1988 A

1990 A

1992 A

1994 A

1997 A

1998 A

2002 B

Change

in SPIRE
Data: series resistance changes single modules

 Dark & Light Slopes dV/dJ plotted vs.

 1/J for dark data read along lower 

ordinate axis

 1/(J+JLight) for light data, read along 

upper ordinate axis

 2002 B in upper pane (‘02, ‘05, ’08) 

1998 A in lower pane (‘99, ‘02, ’07) 

 For 2002 B no increase in Rse 

intercept in both dark & light data 

over time

curvature suggestive of other effects

 For 1998 A substantial increase in Rse 

intercept in dark (~ 4 Ω-cm2) & some 

in light (1-2 Ω-cm2) data with time

1/J (cm 2/A)

dV/dJ (

Ω-cm2)

0

5

10

15

20

25

CIS B: 2002

Lit-08

Lit-02

Drk-05 Lit-05

Drk-02

Drk-08

0 100 200 300 400

400 300 200 100 0 1/[J + J L] (cm2/A)

CIS A: 1998

 dV/dJ (

Ω-cm2)

0

5

10

15

20

25

1/[J + JL] (cm2/A)

0 100 200 300 400

1/J (cm2/A)

Lit-99

Lit-02

Lit-07

Drk-99

Drk-02

Drk-07

400 300 200 100 0
Series resistance data, STC/dark I-V on LACSS

 1988 A 

 Dark increase ~ 1.2 to 2.0 Ω-cm2

 Light increase ~ 0.8 to 1.4 Ω-cm2

 1994 A #1 & #2

 Dark increase ~ 2.1–2.8 to 4.5–6 Ω-cm2

 Light increase ~ 1.4 to 2.0 Ω-cm2

 1998 A

 Dark increase: 1.2 to 5 Ω-cm2

 light increase: 1 to 2.8 Ω-cm2 

 1997 A (PERT)

 Dark increase (2002–06): 1 Ω-cm2

 light increase (2002–06): 1⁄2 Ω-cm2

0.0

1.0

2.0

3.0

4.0

5.0

6.0

Jun-99 Jun-00 Jun-01 Jun-02 Jun-03 Jun-04 Jun-05 Jun-06 Jun-07 Jun-08

Rseries (Ohm-cm2

)

1988 A Drk 1988 A Lit

1994 A I Drk 1994 A I Lit

1994 A II Drk 1994 A II Lit

1997 A drk 1997 A Lit

1998 A Drk 1998 A Lit

2002 B Drk 2002 B Lit

 (1997 A) substantial metastable drop in Rs 

of 3.5 or 1 Ω-cm2 for dark or light, while 

module lay indoors 1 year

 Also reflected in performance (in & out)

 2002 B

 Dark 1.5 to 2.3 Ω-cm2

 Light 0.6 to 1.4 Ω-cm2

 2002 B (PERT)

 Dark nearly no change ~ 1.8 Ω-cm2

 light nearly no change ~ 1.5 Ω-cm2

 Rse increases impact type A more than type B 

because of higher Jsc for A (STC)

 ~30 mA/cm2 for A, ~24 mA/cm2 for B

 Dark (filled), Light (open) 

symbols

 Long-term exposure rack 

modules shown, with A & B 

from PERT occasionally 

tested on LACSS

 Manually drawn trend lines 

shown as guide
Diode J0, A factors, STC/dark I-V on LACSS

 A from dark or light dV/dJ–1/J data; 

 J0 from dark Log(Jcor) –Vcor

 A modules (over 8-years period)

 Quality factors changes between 

negligible to 20% increases 

 Dark J0 increases small, highest factor 

of x2 

 B modules (over 5-year period)

 Quality factors show more substantial 

gain, 25%-30% 

 J0 changes by mult factor up to 40

 More detail picture show 2-diode type 

behavior, primary weakening

Jun-99 Jun-00 Jun-02 Jun-04 Jun-06 Jun-08

10-7

10-6

10-5

10-8

J0 (A/cm2

) 10-4 1988 A Drk 1994 A I Drk

1994 A II Drk 1997 A drk

1998 A Drk 2002 B Drk

ctor 3.0

3.5 1988 A Lit

1994 A I Lit

1994 A II Lit

1997 A Lit

1998 A Lit

2002 B Lit

1988 A Drk

1994 A I Drk

1994 A II Drk

1997 A drk

1998 A Drk

2002 B Drk

Diode Quality Fac 1.5

2.0

2.5

Jun-99 Jun-00 Jun-02 Jun-04 Jun-06 Jun-08

1.0

1.5
Sample PERT 1997 A Data: Across Irradiance

 Roc(Irr), FF(Irr) & Voc(Irr) from top to bottom

 Segregated data by irradiance bins ±25 W/m2, 

 Linear regression with Tmod, evaluated at 25°C; 

 data partitioned into 3-month semesters 2002-08

 Examine 3 irradiance ranges, each spanning ±75 

W/m2 , at low (250 W/m2), mid (500 W/m2) , & 

high (1000 W/m2) intensities

 Sample data for Fall 2002, Fall 2004 & Spring 2008 

 Voc vs. Irradiance data: slight drop with time, 

 FF vs. Irradiance data

 Peak in FF at 250 W/m2, followed by linear 

decline toward high irradiance typical of many 

modules consistent with compromise between 

series resistance loss vs. optical transparency

 exhibit 5% relative decline for all irradiance 

above 250 W/m2, consistent with series 

resistance (Rse) increase 

 Roc vs. 1/ Isc data intercept gives Rse 

 increase of about 0.6 ohms, or 50% relative

Irradiance (W/m2)

1 / Isc (A-1)

Fall '02

Fall '04

Spring '08

0 100 200 300 400 500 600 700 800 900 1000 1100

Roc (Ohms)

0.0 0.5 1.0 1.5 2.0 2.5 3.0

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

Rse

Irr > 300 W/m2

Fall '02

Fall '04

Spring '08

19

20

21

22

23

24

25

26

Voc (volts)

56

57

58

59

60

61

62

63

64

65

FF (%)

± 75

W/m2

± 75

W/m2

± 75

W/m2
PERT 1997 A Data: Power Parameters vs. time

 Data in 3 irradiance bands, low to high 

irradiance, plotted vs. time

 Voc & Jsc normalized to cell level

 Performance (δEff /δt) loss rates

1.3 %/yr to 1.5 %/yr all 3 bands

 FF degradation rates dominate loss

0.6 %/yr to 0.8 %/yr

Lower FF at high irradiance coupled with 

higher FF at low irradiance consistent with 

series resistance as failure mode

 Jsc decline next discernable loss mode

0.4%/yr at 1000 W/m2, or 0.7%/yr lower 

irradiance

1997 A

Jsc (mA/cm2) Efficiency (%) Cell Voc (mV) FF (%)

5

6

7

8

9

10

5

10

15

20

25

30

56

58

60

62

64

66

400

450

500

550

1000 W

500 W

250 W

1000 W

500 W

250 W

1/02 1/03 1/04 1/05 1/06 1/07 1/08
Sample PERT 2002 B Data: Across Irradiance

 Roc(Irr), FF(Irr) & Voc(Irr) from top to bottom

 Segregated data by irradiance bins ±25 W/m2, 

 Linear regression with Tmod, evaluated at 

25°C; 

 data partitioned into 3-month semesters 2002- 08

 Examine 3 irradiance ranges, each spanning 

±75 W/m2 , at low (250 W/m2), mid (500 W/m2) 

, & high (1000 W/m2) intensities

 Sample data for Fall 2002, Fall 2004 & Spring 2008 

 Voc vs. Irradiance data: small but discernable drop 

vs. time lately

 FF vs. Irradiance data, between 2002 and 2008

 Plateau behavior in FF from low to high 

increasing irradiance, not typically consistent 

with series resistance loss mode, but Gsh losses

 10 % relative decline at 250 W/m2, 

 5 % relative decline at 500 W/m2, 

 3 % relative decline at 1000 W/m2, 

 Rse: Roc vs. 1/Isc data intercept

 No apparent significant increase 

Irradiance (W/m2)

Voc (volts)

39

41

43

45

47

49

51

53

55

FF (%)

42

44

46

48

50

52

54

56

58

60

62

64

66

68

70

72

0 100 200 300 400 500 600 700 800 900 1000 1100

Fall '02

Fall '04

Spring '08

1 / Isc (A-1)

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Irr > 300 W/m2

Roc (Ohms)

0

1

2

3

4

5

6

7

8

9

10

11

12

Rse

Fall '02

Fall '04

Spring '08

± 75

W/m2

± 75

W/m2

± 75

W/m2
PERT 2002 B Data: Power Parameters vs. time

 Data in 3 irradiance bands, low to high 

irradiance, plotted vs. time

 Voc & Jsc normalized to cell level

 Performance (δEff /δt) loss rates

-2.3 %/yr low, -1.8 %/yr mid, -1.0 %/yr 

high irradiance

 FF degradation rates dominate 

performance loss rates

-1.31 %/yr, -0.80 %/yr, -0.51 %/yr at low, 

mid, high irradiance

Low & mid irradiance losses appear larger 

initially 

 Voc declines ~ -0.4%/yr

 Jsc declines -0.7%/yr at low & mid 7

8

9

10

11

Jsc (mA/cm2) Efficiency (%) Cell Voc (mV) FF (%)

1/02 1/03 1/04 1/05 1/06 1/07 1/08

60

62

64

66

68

70

72

1000 W

500 W

250 W

0

5

10

15

20

25

550

600

650

700

1000 W

500 W

250 W

 2002 B
PERT 1997 A & 2002 B: Rse, A Data vs. time

 Rseries extrapolated for Irr > 300 W/m2 for 

each set Roc(Irr)-1/Isc(Irr) each semester, 

 if regression includes lower Irr does not 

alter results significantly except scatter

 A module

 Rseries degrades (increases) 0.4 to 0.5 

ohms in over 6 years

 Point at Aug-2007 correlates with 

metastable performance

 Diode quality factor degrades (increases) 

at rate ~ 2.5 %/yr 

 B module

 Rseries: statistically no change

 Diode quality factor degrades (increases) 

at rate ~ 0.7 %/yr

R series (Ohm) Diode Quality Factor

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

1997 A

2002 B

1997 A

2002 B

Jan-02 Jan-04 Jan-06 Jan-08
(+ String) Sample HVST2 Data : Across Irradiance

 Roc(Irr), FF(Irr) & Voc(Irr) from top to bottom

 segregated data by irradiance bins ±25 

W/m2

, 3 irradiance ranges, at low, mid, & 

high intensities, regression to evaluate 

parameters at 25°C

 data for Jun’05 thru Apr’08 color coded in 

rainbow-spectral-sequence: 

 red earlier ‘05, blue  latter ‘08

 Voc vs. Irradiance data: 

 slight but palpable drop vs. time 

 FF vs. Irradiance data exhibit 10% relative 

decline between Jun’05 and Apr’08

 Rse: Roc vs. 1/Isc data intercept

 Obvious shift in Rse to higher values vs. 

time by ~ 4-5 ohms

String Roc (Ohms)

0

10

20

30

40

50

60

1 / Isc (A-1)

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8

Irradiance (W/m2)

String Voc (V)

220

230

240

250

260

270

280

290

0 200 400 600 800 1000

FF (%)

52

54

56

58

60

62

64

66

± 75

W/m2

± 75

W/m2

± 75

W/m2

Irr > 300 W/m2

Oct-05

Mar-06

Nov-06

Mar-07

Nov-07

Apr-08

Jun-05

Jan-06

Aug-06

Jan-07

Sep-07

Feb-08

Oct-05

Mar-06

Nov-06

Mar-07

Nov-07

Apr-08

Jun-05

Jan-06

Aug-06

Jan-07

Sep-07

Feb-08
HVST2 array Power Parameters vs. time: (– string)

 Data in 3 select irradiance bands shown, 

 adjacent bands averaged, span ±75 W/m2 

 Time span: Apr. 2005 – Jul. 2008

 Efficiency loss rates moderately high 

 FF degradation rates lead

 Voc degradation also discernable

 initial ~ 284 V (6 V less than + string)

 Some Isc loss rate at high irradiance

Negative string summary loss rates

250 W/m2

(%/yr)

500 W/m2

(%/yr)

1000 W/m2

(%/yr)

Eff -3.7 ±0.95 -3.4 ±0.68 -4.8 ±0.29

FF -3.1 ±0.24 -3.1 ±0.22 -3.7 ±0.30

Voc -0.52 ±0.12 -0.36 ±0.07 -0.30 ±0.09

Isc -0.24 ±0.76 0.15 ±0.66 -0.99 ±0.21

Negative String

1000 W

250 W

500 W

1000 W

250 W

500 W

String Isc (A) String Voc (V) FF (%) Efficiency (%)

0.6

1.0

1.4

1.8

2.2

2.6

5

6

7

8

9

10

250

260

270

280

290

55

57

59

61

63

Apr-05 Apr-06 Apr-07 Apr-08
HVST2 array Power Parameters vs. time: (+ string)

 Data in 3 select irradiance bands shown, 

 adjacent bands averaged, span ±75 W/m2 

 Time span: Apr. 2005 – Jul. 2008

 Efficiency loss rates moderately high, but 

discernable lower than for negative string 

 FF degradation rates lead, then Voc

 Most loss rates smaller than for Voc loss 

lower than negative at high irradiance

 Isc loss at high irradiance

Positive string summary loss rates

250 W/m2

(%/yr)

500 W/m2

(%/yr)

1000 W/m2

(%/yr)

Eff -3.3 ±1.15 -2.0 ±0.83 -3.3 ±0.34

FF -2.2 ±0.31 -2.0 ±0.29 -2.0 ±0.30

Voc -0.45 ±0.12 -0.20 ±0.07 -0.21 ±0.07

Isc -0.93 ±0.86 0.33 ±0.77 -1.13 ±0.29

Positive String

String Isc (A) String Voc (V) FF (%) Efficiency (%)

0.6

1.0

1.4

1.8

2.2

2.6

5

6

7

8

9

10

250

260

270

280

290

55

57

59

61

63

Apr-05 Apr-06 Apr-07 Apr-08

1000 W

250 W

500 W

1000 W

250 W

500 W
HVST2 ± strings: Rse, A Data vs. time

 Rseries 2005 to 2008

 Both strings start out at nearly 

identical values (~ 9 ohms), but 

increase 4-6 ohms with time

Growth in negative string’s Rse 

outpaces the positive string by 2 ohms in 

3 years

 intercept derived for Irr > 300 W/m2

but including lower intensities produces 

similar results with larger scatter

 Diode Q factors degradation (growth) 

rates:

 -string: 12 %/yr

 +string 7.5 %/yr

Neg String

Pos String

Neg String

Pos String

String series resistance

(Ohm)

Average diode quality

factor per cell

0

2

4

6

8

10

12

14

16

18

1.0

1.5

2.0

2.5

3.0

3.5

Apr-05 Apr-06 Apr-07 Apr-08
Conclusions: Performance Loss Rates @ STC

 Long-term exposure rack modules:

 Type A, SPIRE 

(1 of 1988, 2 each 1990, 1992, 1994, 1998)

Predominantly FF losses via Rse increases, followed by Voc loss

Isc losses likely not significant

 Type 2002 B 

(2 modules SPIRE & LACSS, includes one on PERT)

Loss rate in FF counter-balanced by increase rate in Voc

Module Type ∆Voc/Voc

(%/yr)

∆Isc/Isc 

(%/yr)

∆FF/FF

(%/yr)

∆ Eff / Eff 

(%/yr) TIMELINE

1988 A -0.25% 0.36% -1.09% -0.90% Nov-90 –Mar-08

1990 A -0.02% 0.01% -0.24% -0.26% Oct-91–Mar-08

1992 A -0.05% 0.19% -0.55% -0.43% Aug-92–Mar-08

1994 A -0.08% -0.11% -0.84% -1.01% Mar-95–Mar-08

1998 A -0.24% -0.15% -1.89% -2.19% Jan-99–Mar-08

2002 B 0.57% -0.16% -0.83% -0.40% Aug-02–Mar-08
Conclusions: Performance Loss Rates PERT 

 Average  loss rate 1997 A: -1.4 %/yr, 

 FF declines from Rse increase dominate performance loss

 Jsc decline next more important sizeable loss

 Average  loss rate 2002 B: -1.7 %/yr

 FF declines dominate performance loss, likely from shunt increase, 

 Jsc decline next important sizeable loss, but Voc loss larger at high irradiance

 Average over 3 irradiance windows (250 W/m2, 500 W/m2, 1000 W/m2)

Module 250 W/m2

 

(%/yr) 

500 W/m2 

(%/yr) 

1000 W/m2 

(%/yr) 

Eff -1.3 ± 0.08 -1.5 ±0.04 -1.3 ±0.03

FF -0.60 ±0.13 -0.75 ±0.13 -0.84 ±0.20

Voc -0.07 ±0.00 -0.05 ±0.00 -0.13 ±0.00

Jsc

1997 A

-0.68 ±0.06 -0.71 ±0.06 -0.37 ±0.04

Module 250 W/m2

 

(%/yr) 

500 W/m2 

(%/yr) 

1000 W/m2 

(%/yr) 

Eff -2.3 ±0.09 -1.8 ±0.04 -1.0 ±0.02

FF -1.31 ±0.29 -0.80 ±0.15 -0.51 ±0.09

Voc -0.45 ±0.00 -0.35 ±0.00 -0.38 ±0.00

Jsc

2002 B

-0.74 ±0.04 -0.72 ±0.04 -0.13 ±0.05
Conclusions: Performance Loss Rates HVST2 

 Decline rates averaged  Negative string degradation at -4.0 %/yr

 Decline rates averaged  Positive string degradation at -2.9 %/yr

 High-voltage stress may lead to higher degradation in these A (2003) modules 

 Higher loss may also be result of manufacturer process, probably both

 FF decline & Rseries increases dominate performance loss/failure mode: 

 11%/yr and 20%/yr, for the positive and negative strings, respectively

 Degradation rates consistent with earlier analysis done via PTC regression method

 Average over 3 irradiance windows (250 W/m2, 500 W/m2, 1000 W/m2)

250 W/m2

(%/yr)

500 W/m2

(%/yr)

1000 W/m2

(%/yr)

Eff -3.3 ±1.15 -2.0 ±0.83 -3.3 ±0.34

FF -2.2 ±0.31 -2.0 ±0.29 -2.0 ±0.30

Voc -0.45 ±0.12 -0.20 ±0.07 -0.21 ±0.07

Isc -0.93 ±0.86 0.33 ±0.77 -1.13 ±0.29

250 W/m2

(%/yr)

500 W/m2

(%/yr)

1000 W/m2

(%/yr)

Eff -3.7 ±0.95 -3.4 ±0.68 -4.8 ±0.29

FF -3.1 ±0.24 -3.1 ±0.22 -3.7 ±0.30

Voc -0.52 ±0.12 -0.36 ±0.07 -0.30 ±0.09

Isc -0.24 ±0.76 0.15 ±0.66 -0.99 ±0.21
Acknowledgements

 This work was supported by 

the U.S. Department of Energy 

contract No. DE-AC36-99GO10337

 Thank you for your attention