Solar cell efficiency tables

PROGRESS IN PHOTOVOLTAICS: RESEARCH AND APPLICATIONS, VOL 1, 25-29 (1993)

Research

Solar Cell Eficiency Tables Martin A. Green' and Keith Emery2

' Centre for Photoooltaic Devices und Systems, University of New South

Wales, Kensington 2033, Australia;

' National Renewable Energy Laboratory, Golden, Colorado 80401, U S A

One regular feature planned for Progress in Photovoltaics is the publishing of solar cell and module eflciency tables summarizing the highest independently confirmed results for diflerent technologies. These tables are expected to be of interest not only to researchers directly involved in these areas but also to those less directly involved but interested in being kept informed of the latest results with each of the diflerent technologies or interested in an authoritative summary of these results. Other desirable outcomes may be the encouragement of researchers to seek independent confirmation of research results and the further simulation of intercomparison of measurements between designated cell test centres. Guidelines for inclusion of results into these tables are outlined and the first set of tables of results conforming to these guidelines are published.

INTRODUCTION

T

abulations of the best results demonstrated by different solar cell technologies are expected to be of interest to a wide cross-section of journal readers. To be most useful, it is important that these efficiencies be measured under standardized test conditions. Also, given the difficulties that can arise in efficiency measurement, even for the wary, it is proposed that only measurements that have been confirmed independently at a recognized cell test centre be included in the table. In this way, it is hoped to encourage researchers to have important results confirmed independently, to facilitate mechanisms for obtaining such independent confirmation and to stimulate further intercomparison of cell measurements between different recognized test centres. '

GUIDELINES The most important criterion for inclusion of results into the tables is that they must have been measured by a recognized test centre listed in the Appendix (this list will be updated periodically). Round-robin testing between these designated test centres suggests that measurements at different centres agree to within about 2% (relative) for crystalline and multicrystalline silicon cells, increasing to about 5% for amorphous silicon cells.' Increased differences were noted for modules.' The measurement uncertainty of tandem cell efficiency is larger because even if the short-circuit current can be determined accurately, the fill factor and efficiency are a function of the relative spectral irradiance of the light source. The majority of these centres are capable of non-concentrator cell measurements with respect to the standard set of terrestrial reporting conditions defined by a tabular spectral irradiance distribution (IEC 904-3 or ASTM E892-87), a total irradiance distribution of 1000 W m-' and a temperature of 25°C.2-10.Some are equipped for concentrator measurements under the direct normal reference spectrum (ASTM standard E891-87)j or for space cell testing under the Air Mass 0 (AMO) spectrum. 1062-7995/93/0 10025-05 $07.50 1993 by John Wiley & Sons, Ltd

I('

Received 22 September 1992 Revised 29 September 1992

M . A . GREEN A N D K . EMERY

26

'

The area of the cell or module is an important parameter in determining efficiency.' It is also important that this area be measured by the test centre to an accuracy of better than 0.5%. The areas used should conform to one of the three following classifications for the purposes of the present tables (these definitions are provisional, pending wider discussion within the photovoltaic community, and may have been different in the past): (0 Total area. This is the preferred area for reporting of results and equals the total projected area of the cell or module (the area that would be measured by taking a photograph of the device against a white background and measuring the area of the background shaded by the device). For the case of a cell attached to glass, the total area would be the area of the glass sheet. (ii) Aperture area. In this measurement, the device under test is masked so that the illuminated area is smaller than the total cell or module area, but all essential components of the device, such as busbars, fingers and interconnects, lie within the masked area. (Masking is not required if it can be demonstrated that areas outside the aperture area are not responsive to light or are not steering light onto active areas.) (iii) Designated illumination area. In this case, the cell or module is masked to an area smaller than the total device area, but major cell or module components lie outside the masked area. For example, for a concentrator cell, the cell busbars would lie outside of the area designated for illumination and this area classification would be the most appropriate. (Again, masking is not required if it can be demonstrated that areas outside the designated illumination area are not responding to light.) Active area efficiencies will not be included. Results will be reported for cells and modules made from different semiconductors and for subcategories within each semiconductor grouping (e.g. crystalline, Table I. Confirmed terrestrial cell efficiencies measured under the global AM1.5 spectrum (loo0 W m-') at 25°C Classification"

E f f i ~ . ~Area' (%) (cm2)

Kc

Jsc

(V)

(mA cm-')

FFd Test centre (%) (and date)

Description

Silicon cells

Si (crystalline) Si (moderate area) Si (multicrystalline) Si (multicrystalline) Si (thin film)

23.1 21.6 17.7 17.3 14.9

4.03 (ap) 37.5 (da) 1.00 (ap) 4.12 (t) 1.02 (ap)

0.696 0.698 0.623 0.608 0.600

40.9 39.5 35.6 35.7 31.4

81.0 78.4 71.2 73.7 79.2

Sandia' (2/90) Sandia' (5/90) NREL (1/92) NREL (8/89) Sandia' (12/88)

UNSW PERL Stanford point contact Georgia Tech UNSW PESC AstroPower (Si-film)

I I I - V cells GaAs (crystalline) GaAs (Ge substrate) GaAs (thin film) InP (crystalline)

25.1 24.3 23.3 21.9

3.91 (t) 4.00 (t) 4.00 (ap) 4.02 (t)

1.022 1.035 1.011 0.878

28.2 27.6 27.6 29.3

87.1 85.3 83.8 85.4

NREL (3/90) NREL (3/89) NREL (4/90) NREL (4/90)

Kopin, AlGaAs window ASEC, AlGaAs window Kopin 5 pm CLEFT Spire, epitaxial

15.8 13.7 11.5

1.05 (ap) 0.99 (ap) 1.08 (ap)

0.843 0.546 0.879

25.1 36.7 18.8

74.5 63.4 70.1

NREL (7/90) NREL (7/92) NREL (4/81)

South Florida CSVT Boeing So1arex

27.6 27.3 25.8 14.6 12.4

0.50 (t) 0.25 (t) 4.00 (t) 2.40 (ap) 0.27 (t)

2.403 2.292

14.0 13.6

83.4 87.5

-

-

-

NREL NREL NREL NREL NREL

Varian monolithic NREL monolithic Kopin/Boeing 4 terminal ARC0 4 terminal Energy conversion devices

Other cells

CdTe (thin film) CIGS (thin film) a-Si (thin film) Multijunction cells

GaAIAs/GaAs GaInP/GaAs GaAs/CIS (thin film) a-Si/CIGS (thin film) a-Si/a-Si/a-SiCe

2.541

7.0

-

70.0

(3/89) (8/89) (11/89)

(6/88) (2/88)

"CIS = CuInSe,; CIGS = CuInGaSe,; a-Si = amorphous silicon/hydrogen alloy. Effic. = efficiency. (t) = total area; (ap) = aperture area; (da) = designated illumination area. FF = 811 factor. ' Measurements corrected from originally measured values due to Sandia recalibration in January 1991.

27

SOLAR CELL EFFICIENCY TABLES

Table 11. Confirmed terrestrial module efficiencies measured under the global AM1.5 spectrum (loo0 W m-') at 25°C EfIicd

K C

FF'

Classification"

(%I

(V)

(%I

Test centre (and date)

Description

Si (crystalline) CIGS (thin film) a-Si/a-Si (thin tandem)b a-Si (thin film) CdTe (thin film)' a-Si (thin film large)

18.2 11.1 10.1 9.8 8. I 6.8

10.3 25.9 53.6 42.4 21.0 22.6

81 64 13 64 55 71

Sandia (12/88) NREL (6/88) NREL (5/92) NREL (2/90) NREL (9/91) NREL (6/88)

UNSW laser-grooved, 16 cells ARCO, 55 cells Fuji electric Solarex Photon Energy ARCO

1.64 0.637 0.310 0.337 0.573 2.10

CIGS = CuInGaSe,; a-Si = amorphous silicon/hydrogen alloy. bThis module was 8.97; efficient after 980 h of continuous I sun illumination at 50°C under load (most a-Si modules degrade by 15-20% under these conditions). Output varies with premeasurement condltions and bias rate. Efficiency rate taken with maximum power point tracking. Effic. = efficiency. ' (ap) = aperture area. IFF = fill factor.

Table 111. Terrestrial concentrator cell and module efficiencies measured under the direct beam AM 1.5 spectrum (loo0W/m2) at a cell temperature of 25°C Effic." Classification

(%I

Areab (cm')

Concentration (suns)

Test centre (and date)

Description Varian (prism cover) Stanford point contact UNSW PERL UNSW laser-grooved

Single cells

GaAs Si Si (moderate area) Si (large)

21.5 26.5 24.8 21.6

0.126 (da) 0.150 (da) 1.56 (da) 20.0 (da)

205 140 21 11

Sandia' Sandia' Sandia' Sandia'

32.6 31.8 30.2 29.6

0.053 (da) 0.63 (da) 0.53 (da) 0.317 (da)

100 50 40 350

Sandia' (10/89) NREL (8/90) NREL (10/76) Sandia' (9/88)

Boeing: mech. stack NREL; monolithic 3 terminal NREL; stacked 4 terminal Sandia: mech. stack

Sandia (4/89)

Sandia/UNSW/ENTECH

(4/88) (5/87) ( /88) ( /90)

Multijunction cells

GaAs/GaSb InP/GaInAs GaAs/GaInAsP GaAs/Si Modules

Si

20.3

80

a Effic. = efficiency. b(ap)= aperture area; (da) = designated illumination area. ' Measurements corrected from originally measured values due to Sandia recalibration in January 1991

polycrystalline and thin film). Cell area must be at least 1 cmz for non-concentrating cells, although results for areas as low as 0.25 cm2 will be eligible for concentrator and, at least in the near term, for tandem cells. Given that cell and module efficiency normally decreases with increasing area, additional subcategories will be included, depending upon area. Although some flexibility is desirable in this area, subcategory boundaries will be roughly at 1 , l O and 100 cm2 for non-concentrator cells, 800 and 3000 cm2 for modules and 0.25, 2 and 20 cm2 for concentrator cells. Table I shows the collected results for terrestrial cells under the global Air Mass 1.5 spectrum, Table I1 shows the same results for modules and Table 111 shows the results for concentrator cells. The data for these tables were obtained by surveying the test centres of the Appendix. Information updating these entries is welcome at any time and should be sent to one of the authors.

M.A. GREEN AND K. EMERY

28

Tables are planned to be published frequently in this journal without the same degree of explanation as in the present issue. New entries since the last table published will be highlighted. It is also proposed that round-robin testing of cells of an efficiency level comparable to those appearing in the tables at designated test centres be organized and the results published. This would provide feedback of interest to these centres and give readers some idea of the uncertainties involved in the reported measurements. While the information in the tables is provided in good faith, the authors, editors and publishers cannot accept direct responsibility for any errors or omissions. 1 YPE.1'DI.Y List of designated test centres

CEC Joint Research Centre, 1-21020 Ispra (Varese), Italy. Contact: Dr Heinz Ossenbrink. Tel.: (39) 332-789-196; Fax: (39) 332-789-268. (Terrestrial cells and modules) Fraunhofer-Institut fur Solare Energiesysteme, Oltmannsstrasse 22, D-7800 Freiburg, Germany. Contact: Drs Klaus Heidler and Klaus Bucher. Tel.: (49) 761-4014-145;Fax: (49) 761-4014-100. (Terrestrial, concentrator and space cells and modules) JMI Institute, Kanto Office, Solar Cell Test Research Laboratory, 21-25 Kinuta, 1-Chome, Setagaya-ku, Tokyo 157, Japan. Contact: Dr Fumiaki Nagamine. Tel.: (81) 3-3416-5560; Fax: (81) 3-3749-3505. (Terrestrial cells and modules) NASA Lewis Research Center, MS 301-1, 21000 Brookpart Road, Cleveland, O H 44135, USA. Contact: Dr David Brinker, Senior Research Engineering. Tel: (1) 216-433-2236;Fax: (1) 216-433-6106. (AM0 cell measurements) National Renewable Energy Laboratory, 1617 Cole Blvd., Golden, CO 80401, USA. Contact: Mr Keith Emery. Tel.: ( 1 ) 303-231-1032; Fax: (1) 303-231-1381. (Terrestrial and concentrator cells and modules) Physikalisch-Technische Bundesanstalt., Bundesallee 100, D-3300 Braunschweig, Germany. Contact: Dr Juergen Metzdorf. Tel: (49) 531-59 24 100; Fax: (49) 531-59 24 006. (Terrestrial cells and modules) Royal Aircraft Establishment, Defence Research Agency, Farnborough, Hampshire GU14 6TD, UK. Contact: Mr C. Goodbody, Space Technology Dept., P234 Building. Tel.: (44) 252-24461; Fax: (44) 252-377121. (Primarily AM0 calibrations) Sandia National Laboratories, 1515 Eubank SE, Albuquerque, NM 87123, USA. Contact: Mr David King, Division 6224. Tel.: (1) 505-844-8220; Fax: (1) 505-844-6541. (Terrestrial and concentrator cells and modules)

REFER E,Z'CES 1. J. Metzdorf, T. Wittchen, K. Heidler, K. Dehne, R. Shimokawa, F. Nagamine, H. Ossenbrink, L. Fornarini, C.

Goodbody, M.Davies, K. Emery and R. DeBlasio, Objectives and results of the PEP87 round-robin calibration of reference solar cells and modules. Conference Record of the 21st ZEEE Photovoltaic Specialists Conference, Kissimimee, May 1990, pp. 952-959.

S O L A R C E L L EFFICIENCY T A B L E S

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2. Standard for Terrestrial Solar Spectral Irradiance Tables at Air Mass 1.5 for a 37" Tilted Surface, ASTM Standard E892, Vol. 12.02. ASTM, Philadelphia, PA. 3. Standard.for Terrestrial Direct Normal Solar Spectral Irradiance Tables for Air Mass 1.5, ASTM Standard E891, Vol. 12.02. ASTM, Philadelphia, PA. 4. Measurement Principles ,for Terrestrial P V Solar Devices with Reference Spectral Irradiance Data, International Electrotechnical Commission Standard 904-3. IEC (1989). 5. Photovoltaic Devices Part 1 Measurement of Photovoltaic Current- Voltage Characteristics, International Electrotechnical Commission Standard 904-1. IEC (1989). 6. Standard Methods of Testing Electrical Performance of Non-concentrator Terrestrial Photovoltaic Modules and Arrays using Reference Cells, ASTM Standard E1036, Vol. 12.02. ASTM, Philadelphia, PA. 7. Standard Methods qf Testing Electrical Performance of Photovoltaic Cells using Reference Cells, ASTM Standard E948, Vol. 12.02. ASTM, Philadelphia, PA. 8. Standard Procedures for Terrestrial Photovoltaic Measurements, CEC 101, Issue 2, EUR 7078, EN. Commission of the European Community, Brussels (1981). 9. K. A. Emery, C. R. Osterwald and C. V. Wells, Uncertainty analysis of photovoltaic efficiency measurements. Proc. 19th IEEE Photovoltaic Specialists Con$, New Orleans, L A , 4-8 M a y 1987, pp. 153-159. 10. K. Heidler and J. Beier, Uncertainty analysis of PV efficiency measurements with a solar simulator: spectral mismatch, non-uniformity and other sources of error. Proc. 8th European Solar Energy Con$, Florence, Italy, 9-12 M a y 1988, pp. 554-559. 11. K. Emery and C. Osterwald, Efficiency measurements and other performance-rating methods. In Current Topics in Photovoltaics, Vol. 3, ed. by T. Coutts and J. Meakin, Chapt. 4, pp. 301-350. Academic Press, New York (1988).