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Band-Gap-Engineered Architectures for High-Efficiency Multijunction Concentrator Solar Cells Richard R. King, A. Boca, W. Hong, X.-Q. Liu, D. Bhusari, D. Larrabee, K. M. Edmondson, D. C. Law, C. M. Fetzer, S. Mesropian, and N. H. Karam

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  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

1

Band-Gap-Engineered Architectures for High-Efficiency Multijunction Concentrator Solar Cells

Richard R. King, A. Boca, W. Hong, X.-Q. Liu, D. Bhusari, D. Larrabee,

  • K. M. Edmondson, D. C. Law, C. M. Fetzer,
  • S. Mesropian, and N. H. Karam

Spectrolab, Inc.

A Boeing Company

24th European Photovoltaic Solar Energy Conference

  • Sep. 21-25, 2009

Hamburg, Germany

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SLIDE 2
  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

2

  • Carl Osterwald, Keith Emery, Larry Kazmerski,

Martha Symko-Davies, Fannie Posey-Eddy, Holly Thomas, Manuel Romero, John Geisz, Sarah Kurtz – NREL

  • Rosina Bierbaum – University of Michigan, Ann Arbor
  • Pierre Verlinden, John Lasich – Solar Systems, Australia
  • Kent Barbour, Russ Jones, Jim Ermer, Peichen Pien,

Dimitri Krut, Hector Cotal, Mark Osowski, Joe Boisvert, Geoff Kinsey, Mark Takahashi, and the entire multijunction solar cell team at Spectrolab

This work was supported in part by the U.S. Dept. of Energy through the NREL High-Performance Photovoltaics (HiPerf PV) program (ZAT-4-33624-12), the DOE Technology Pathways Partnership (TPP), and by Spectrolab.

Acknowledgments Acknowledgments

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SLIDE 3
  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

3

  • Solar cell theoretical efficiency limits

– Opportunities to change ground rules for higher terrestrial efficiency – Cell architectures capable of >70% in theory, >50% in practice

  • Metamorphic semiconductor materials

– Control of band gap to tune to solar spectrum

Outline Outline

Tunnel Junction

Top Cell

Wide-Eg Tunnel

Middle Cell p-GaInP BSF p-GaInP base n-GaInAs emitter n+-Ge emitter p-AlGaInP BSF n-GaInP emitter n-AlInP window n+-GaInAs contact AR p-Ge base and substrate

contact

p-GaInAs step-graded buffer Bottom Cell

p++-TJ n++-TJ

p-GaInAs base

nucleation

n-GaInP window

p++-TJ n++-TJ Tunnel Junction

Top Cell

Wide-Eg Tunnel

Middle Cell p-GaInP BSF p-GaInP base n-GaInAs emitter n+-Ge emitter p-AlGaInP BSF n-GaInP emitter n-AlInP window n+-GaInAs contact AR p-Ge base and substrate

contact

p-GaInAs step-graded buffer Bottom Cell

p++-TJ n++-TJ

p-GaInAs base

nucleation

n-GaInP window

p++-TJ n++-TJ
  • High-efficiency terrestrial concentrator cells

– Metamorphic (MM) and lattice-matched (LM) 3-junction solar cells with >40% efficiency – 4-junction MM and LM concentrator cells – Inverted metamorphic structure, semiconductor bonded technology (SBT) for MJ terrestrial concentrator cells

  • The solar resource and concentrator photovoltaic (CPV)

system economics

0.75-eV GaInAs cell 5 1.1-eV GaInPAs cell 4

semi- conductor bonded interface

1.4-eV GaInAs cell 3 1.7-eV AlGaInAs cell 2 2.0-eV AlGaInP cell 1

metal gridline

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SLIDE 4
  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

4

High-Efficiency Multijunction Cell Architectures

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  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

5

Theoretical 95% Carnot eff. = 1 – T/Tsun T = 300 K, Tsun ≈ 5800 K 93%

  • Max. eff. of solar energy conversion

= 1 – TS/E = 1 – (4/3)T/Tsun (Henry) 72% Ideal 36-gap solar cell at 1000 suns (Henry) 56% Ideal 3-gap solar cell at 1000 suns (Henry) 50% Ideal 2-gap solar cell at 1000 suns (Henry) 44% Ultimate eff. of device with cutoff Eg: (Shockley, Queisser) 43% 1-gap cell at 1 sun with carrier multiplication (>1 e-h pair per photon) (Werner, Kolodinski, Queisser) 37% Ideal 1-gap solar cell at 1000 suns (Henry) 31% Ideal 1-gap solar cell at 1 sun (Henry) 30% Detailed balance limit of 1 gap solar cell at 1 sun (Shockley, Queisser) Measured 3-gap GaInP/GaInAs/Ge LM cell, 364 suns (Spectrolab) 41.6% 3-gap GaInP/GaInAs/Ge MM cell, 240 suns (Spectrolab) 40.7% 3-gap GaInP/GaAs/GaInAs cell at 1 sun (NREL) 33.8% 1-gap solar cell (silicon, 1.12 eV) at 92 suns (Amonix) 27.6% 1-gap solar cell (GaAs, 1.424 eV) at 1 sun (Kopin) 25.1% 1-gap solar cell (silicon, 1.12 eV) at 1 sun (UNSW) 24.7%

References

  • C. H. Henry, “Limiting efficiencies of ideal single and multiple energy gap terrestrial

solar cells,” J. Appl. Phys., 51, 4494 (1980).

  • W. Shockley and H. J. Queisser, “Detailed Balance Limit of Efficiency of p-n Junction

Solar Cells,” J. Appl. Phys., 32, 510 (1961).

  • J. H. Werner, S. Kolodinski, and H. J. Queisser, “Novel Optimization Principles and

Efficiency Limits for Semiconductor Solar Cells,” Phys. Rev. Lett., 72, 3851 (1994).

  • R. R. King et al., "Band-Gap-Engineered Architectures for High-Efficiency

Multijunction Concentrator Solar Cells," 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009.

  • R. R. King et al., "40% efficient metamorphic GaInP / GaInAs / Ge multijunction solar

cells," Appl. Phys. Lett., 90, 183516 (4 May 2007).

  • M. Green, K. Emery, D. L. King, Y. Hishikawa, W. Warta, "Solar Cell Efficiency Tables

(Version 27)", Progress in Photovoltaics, 14, 45 (2006).

  • A. Slade, V. Garboushian, "27.6%-Efficient Silicon Concentrator Cell for Mass

Production," Proc. 15th Int'l. Photovoltaic Science and Engineering Conf., Beijing, China, Oct. 2005.

  • R. P. Gale et al., "High-Efficiency GaAs/CuInSe2 and AlGaAs/CuInSe2 Thin-Film

Tandem Solar Cells," Proc. 21st IEEE Photovoltaic Specialists Conf., Kissimmee, Florida, May 1990.

  • J. Zhao, A. Wang, M. A. Green, F. Ferrazza, "Novel 19.8%-efficient 'honeycomb'

textured multicrystalline and 24.4% monocrystalline silicon solar cells," Appl.

  • Phys. Lett., 73, 1991 (1998).

Maximum Solar Cell Maximum Solar Cell Efficiencies Efficiencies

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  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

6

Metamorphic (MM) Metamorphic (MM) 3 3-

  • Junction Solar Cell

Junction Solar Cell

Tunnel Junction

Top Cell

W i d e

  • E

g T u n n e l

Middle Cell p-GaInP BSF p-GaInP base n-GaInAs emitter n+-Ge emitter p-AlGaInP BSF n-GaInP emitter n-AlInP window n+-GaInAs contact AR p-Ge base and substrate

contact

p-GaInAs step-graded buffer B

  • t

t

  • m

C e l l

p++-TJ n++-TJ

p-GaInAs base

nucleation

n-GaInP window

p++-TJ n++-TJ

Tunnel Junction

Top Cell

W i d e

  • E

g T u n n e l

Middle Cell p-GaInP BSF p-GaInP base n-GaInAs emitter n+-Ge emitter p-AlGaInP BSF n-GaInP emitter n-AlInP window n+-GaInAs contact AR p-Ge base and substrate

contact

p-GaInAs step-graded buffer B

  • t

t

  • m

C e l l

p++-TJ n++-TJ

p-GaInAs base

nucleation

n-GaInP window

p++-TJ n++-TJ

Lattice-Mismatched

  • r Metamorphic (MM)

0.05 0.1 0.15 0.2 0.25 0.3 0.5 1 1.5 2 2.5 3 3.5

Voltage (V)

Current Density / Incident Intensity (A/W)

MJ cell subcell 1 subcell 2 subcell 3

  • Metamorphic growth of upper two subcells, GaInAs and GaInP
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  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

7

10 20 30 40 50 60 70 80 90 100 300 500 700 900 1100 1300 1500 1700 1900

Wavelength (nm) Current Density per Unit Wavelength (mA/(cm 2μm))

10 20 30 40 50 60 70 80 90 100

External Quantum Efficiency (%)

AM1.5D, low-AOD AM1.5G, ASTM G173-03 AM0, ASTM E490-00a EQE, lattice-matched EQE, metamorphic

External QE of LM and MM External QE of LM and MM 3 3-

  • Junction Cells

Junction Cells

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  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

8

1.3 1.4 1.5 1.6 1.7 1.8 1.9 2 2.1 1.0 1.1 1.2 1.3 1.4 1.5 1.6

Eg2 = Subcell 2 Bandgap (eV) Eg1 = Subcell 1 (Top) Bandgap (eV) . Disordered GaInP top subcell Ordered GaInP top subcell

38% 54% 42% 46% 50% 52%

3-junction Eg1/ Eg2/ 0.67 eV cell efficiency

240 suns (24.0 W/cm2), AM1.5D (ASTM G173-03), 25oC Ideal efficiency -- radiative recombination limit

40.7% 40.1%

48% 44% 40%

MM LM

Metamorphic (MM) Metamorphic (MM) 3 3-

  • Junction Solar Cell

Junction Solar Cell

  • Metamorphic GaInAs and GaInP subcells bring band gap combination

closer to theoretical optimum

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  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

9

Concentrator cell light I-V and efficiency independently verified by J. Kiehl, T. Moriarty, K. Emery – NREL

  • First solar cell of

any type to reach

  • ver 40% efficiency

Spectrolab Metamorphic GaInP/ GaInAs/ Ge Cell

Voc = 2.911 V Jsc = 3.832 A/cm2 FF = 87.50% Vmp = 2.589 V

Efficiency = 40.7% ± 2.4%

240 suns (24.0 W/cm2) intensity 0.2669 cm2 designated area 25 ± 1°C, AM1.5D, low-AOD spectrum

Ref.: R. R. King et al., "40% efficient metamorphic GaInP / GaInAs / Ge multijunction solar cells,"

  • Appl. Phys. Lett., 90, 183516, 4 May 2007.

Record Record 40.7%

40.7%-

  • Efficient

Efficient Concentrator Solar Cell Concentrator Solar Cell

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SLIDE 10
  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

10

Growth on Ge or GaAs substrate, followed by substrate removal from sunward surface

Growth Direction

cap

1.9 eV (Al)GaInP subcell 1 1.4 eV GaInAs subcell 2 graded MM buffer layers 1.0 eV GaInAs subcell 3 Ge or GaAs substrate Ge or GaAs substrate

cap

Metamorphic (MM) 3 Metamorphic (MM) 3-

  • Junction Cells

Junction Cells –– –– Inverted 1.0 Inverted 1.0-

  • eV GaInAs Subcell

eV GaInAs Subcell

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  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

11

1 1.1 1.2 1.3 1.4 1.5 1.6 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3

Eg3 = Subcell 3 Bandgap (eV) Eg2 = Subcell 2 Bandgap (eV) .

48% 53% 44% 46% 50% 52%

3-junction 1.9 eV/ Eg2/ Eg3 cell efficiency

500 suns (50 W/cm2), AM1.5D (ASTM G173-03), 25oC Ideal efficiency -- radiative recombination limitX

51%

Inverted Metamorphic (IMM) Inverted Metamorphic (IMM) 3 3-

  • Junction Cell

Junction Cell

  • Raising band gap of bottom cell from 0.67 for Ge to ~1.0 eV for IMM

GaInAs raises theoretical 3J cell efficiency

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SLIDE 12
  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

12

4 4-

  • Junction Upright Metamorphic

Junction Upright Metamorphic (MM) Terrestrial Concentrator Cell (MM) Terrestrial Concentrator Cell

0.67-eV Ge cell 4 and substrate

transparent buffer

1.2-eV GaInAs cell 3 1.55-eV AlGaInAs cell 2 1.8-eV (Al)GaInP cell 1

metal gridline

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  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

13

1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5

Eg3 = Subcell 3 Bandgap (eV) Eg2 = Subcell 2 Bandgap (eV) .

38% 46% 54% 56% 50% 42%

4-junction 1.9 eV/ Eg2/ Eg3/ 0.67 eV cell efficiency

500 suns (50 W/cm2), AM1.5D (ASTM G173-03), 25oC Ideal efficiency -- radiative recombination limitX

58% 34%

4 4-

  • Junction Cell

Junction Cell Optimum Band Gap Combinations Optimum Band Gap Combinations

  • Lowering band gap of subcells 2 and 3, e.g., with MM materials, gives

higher theoretical 4J cell efficiency

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SLIDE 14
  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

14

5 5-

  • Junction Inverted Metamorphic

Junction Inverted Metamorphic (IMM) Cells (IMM) Cells

transparent buffer

0.75-eV GaInAs cell 5 1.1-eV GaInAs cell 4

transparent buffer

1.4-eV GaInAs cell 3 1.7-eV AlGaInAs cell 2 2.0-eV AlGaInP cell 1

metal gridline

Ge or GaAs growth substrate

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SLIDE 15

Semiconductor Semiconductor-

  • Bonded Technology

Bonded Technology (SBT) Terrestrial Concentrator Cell (SBT) Terrestrial Concentrator Cell

InP growth substrate GaAs or Ge growth substrate 1.4-eV GaInAs cell 3 1.7-eV AlGaInAs cell 2 2.0-eV AlGaInP cell 1 0.75-eV GaInAs cell 5 1.1-eV GaInPAs cell 4 GaAs or Ge growth substrate 1.4-eV GaInAs cell 3 1.7-eV AlGaInAs cell 2 2.0-eV AlGaInP cell 1 1.4-eV GaInAs cell 3 1.7-eV AlGaInAs cell 2 2.0-eV AlGaInP cell 1 GaAs or Ge growth substrate 1.4-eV GaInAs cell 3 1.7-eV AlGaInAs cell 2 2.0-eV AlGaInP cell 1 GaAs or Ge growth substrate semi- conductor bonded interface

metal gridline

0.75-eV GaInAs cell 5 1.1-eV GaInPAs cell 4 1.4-eV GaInAs cell 3 1.7-eV AlGaInAs cell 2 2.0-eV AlGaInP cell 1 semi- conductor bonded interface

metal gridline

– Low band gap cells for MJ cells using high-quality, lattice-matched materials – Epitaxial exfoliation and substrate removal – Formation of lattice- engineered substrate for later MJ cell growth – Bonding of high-band-gap and low-band-gap cells after growth – Electrical conductance of semiconductor-bonded interface – Surface effects for semiconductor-to- semiconductor bonding

  • Wafer bonding for multijunction solar cells

15

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SLIDE 16
  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

16

cap contact AR

(Al)GaInP Cell 1 2.0 eV

wide-Eg tunnel junction

GaInP Cell 2 (low Eg) 1.78 eV

wide-Eg tunnel junction

AlGa(In)As Cell 3 1.50 eV

tunnel junction

Ga(In)As Cell 4 1.22 eV

tunnel junction AR

Ga(In)As buffer

Ge Cell 6 and substrate 0.67 eV

nucleation back contact

wide-Eg tunnel junction

GaInNAs Cell 5 0.98 eV

cap contact AR

(Al)GaInP Cell 1 2.0 eV

wide-Eg tunnel junction

GaInP Cell 2 (low Eg) 1.78 eV

wide-Eg tunnel junction

AlGa(In)As Cell 3 1.50 eV

tunnel junction

Ga(In)As Cell 4 1.22 eV

tunnel junction AR

Ga(In)As buffer

Ge Cell 6 and substrate 0.67 eV

nucleation nucleation back contact

wide-Eg tunnel junction

GaInNAs Cell 5 0.98 eV

0.02 0.04 0.06 0.08 0.1 0.12 0.14 1 2 3 4 5 6 7

Voltage (V)

Current Density / Incident Intensity (A/W)

MJ cell subcell 1 subcell 2 subcell 3 subcell 4 subcell 5 subcell 6

6 6-

  • Junction Solar Cells

Junction Solar Cells

100 200 300 400 500 600 700 0.5 1 1.5 2 2.5 3 3.5 4 Photon Energy (eV) Intensity per Unit Photon Energy (W/m 2 . eV) 0.2 0.4 0.6 0.8 1 1.2 1.4 Photon utilization efficiency .

AM1.5D, ASTM G173-03, 1000 W/m2 Utilization efficiency of photon energy 1-junction cell 3-junction cell 6-junction cell

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  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

17

35% 40% 45% 50% 55% 60% 1 10 100 1000 10000 Incident Intensity (suns) (1 sun = 0.100 W/cm2) Efficiency (%)

Detailed balance limit efficiency Radiative recombination only Series res. and shadowing, optimized grid spacing Normalized to experimental efficiency

500 3J & 4J MM solar cells

3J 3J 3J 4J 4J 4J

Modeled Terrestrial Modeled Terrestrial Concentrator Cell Efficiency Concentrator Cell Efficiency

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  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

18

High-Efficiency Multijunction Cell Results

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  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

19

Tunnel Junction

T

  • p

C e l l

Wide-Eg Tunnel

M i d d l e C e l l p-GaInP BSF p-GaInP base n-Ga(In)As emitter n+-Ge emitter p-AlGaInP BSF n-GaInP emitter n-AlInP window n+-Ga(In)As contact AR p-Ge base and substrate

contact

n-Ga(In)As buffer Bottom Cell

p++-TJ n++-TJ

p-Ga(In)As base

nucleation

Wide-bandgap tunnel junction GaInP top cell Ge bottom cell

n-GaInP window

p++-TJ n++-TJ

Ga(In)As middle cell Tunnel junction Buffer region

T u n n e l J u n c t i

  • n

T

  • p

C e l l

Wide-Eg Tunnel

M i d d l e C e l l p-GaInP BSF p-GaInP base n-GaInAs emitter n+-Ge emitter p-AlGaInP BSF n-GaInP emitter n-AlInP window n+-GaInAs contact AR p-Ge base and substrate

contact

p-GaInAs step-graded buffer Bottom Cell

p++-TJ n++-TJ

p-GaInAs base

nucleation

n-GaInP window

p++-TJ n++-TJ

Lattice-Matched (LM) Lattice-Mismatched

  • r Metamorphic (MM)

LM and MM 3 LM and MM 3-

  • Junction

Junction Cell Cross Cell Cross-

  • Section

Section

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  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

20

New World Record New World Record 41.6% Multijunction Solar Cell 41.6% Multijunction Solar Cell

  • 41.6% efficiency demonstrated for 3J

lattice-matched Spectrolab cell, a new world record

  • Highest efficiency for any type of solar

cell measured to date

  • Independently verified by National

Renewable Energy Laboratory (NREL)

  • Standard measurement conditions

(25°C, AM1.5D, ASTM G173 spectrum) at 364 suns (36.4 W/cm2)

  • Lattice-matched cell structure similar

to C3MJ cell, with reduced grid shadowing as planned for C4MJ cell

  • Incorporating high-efficiency 3J

metamorphic cell structure + further improvements in grid design → strong potential to reach 42-43% champion cell efficiency

Ref.: R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009. Concentrator cell light I-V and efficiency independently verified by C. Osterwald, K. Emery – NREL

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  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

21

24 26 28 30 32 34 36 38 40 42 44 0.1 1.0 10.0 100.0 1000.0

Incident Intensity (suns) (1 sun = 0.100 W/cm2) Efficiency (%) and Voc x 10 (V)

0.78 0.80 0.82 0.84 0.86 0.88 0.90 0.92 0.94 0.96 0.98

Fill Factor (unitless)

Efficiency Voc x 10 Voc fit, 100 to 1000 suns FF

  • At peak 41.6% efficiency → 364 suns, Voc = 3.192 V, FF = 0.887
  • Efficiency still >40% at 820 suns, at 940 suns efficiency is 39.8%
  • Diode ideality factor of 1.0 for all 3 junctions fits Voc well from 100 to 1000 suns

41.6% Solar Cell 41.6% Solar Cell Eff., Voc vs. Concentration Eff., Voc vs. Concentration

41.6%

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  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

22

  • At peak 41.6% efficiency → 364 suns, Voc = 3.192 V, FF = 0.887
  • Series resistance causes drop in Vmp above 400 suns, Voc continues to increase
  • Efficiency still >40% at 820 suns, at 940 suns efficiency is 39.8%

41.6% Solar Cell 41.6% Solar Cell LIV Curves vs. Concentration LIV Curves vs. Concentration

0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.5 1 1.5 2 2.5 3 3.5

Voltage (V)

Current Density / Incident Intensity (A/W)

2.6 6.6 17.6 59.8 127.3 364.2 604.8 940.9

  • Inc. Intensity (suns)

1 sun = 0.100 W/cm2

41.6%

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SLIDE 23
  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

23

Chart courtesy of Larry Kazmerski, NREL

Best Research Cell Best Research Cell Efficiencies Efficiencies

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  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

24

37% 37.5% 38.5% 40% 43%

36 37 38 39 40 41 42 43 Production Cell Efficiency (%) 2007 2008 2009 2010 2015

Year

  • Terrestrial

concentrator cell efficiency

  • Goals in

Technology Pathways Partnership (TPP)

Spectrolab Cell Generations Spectrolab Cell Generations in DOE TPP Program in DOE TPP Program

C4MJ

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  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

25

Spectrolab C1MJ, C2MJ, and Spectrolab C1MJ, C2MJ, and C3MJ Cell Products C3MJ Cell Products

0% 5% 10% 15% 20% 25% 30% 35% 40% 34.0% 34.5% 35.0% 35.5% 36.0% 36.5% 37.0% 37.5% 38.0% 38.5% 39.0% 39.5% Efficiency η at Max. Power % of Population C1MJ C2MJ C3MJ ηAVG = 36.9% ηAVG = 37.5% ηAVG = 38.2% 0% 5% 10% 15% 20% 25% 30% 35% 40% 34.0% 34.5% 35.0% 35.5% 36.0% 36.5% 37.0% 37.5% 38.0% 38.5% 39.0% 39.5% Efficiency η at Max. Power % of Population C1MJ C2MJ C3MJ ηAVG = 36.9% ηAVG = 37.5% ηAVG = 38.2%

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  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

26

Isc (A) Voc (V) FF Eff Average 7.601 3.090 0.845 39.6%

  • Std. dev.

0.135 0.022 0.009 0.8%

35.7% 36.0% 36.3% 36.6% 36.9% 37.2% 37.5% 37.8% 38.1% 38.4% 38.7% 39.0% 39.3% 39.6% 39.9% 40.2% 40.5% 40.8%

5% 3J-MM

Corrected LIV Data for Prototype 3J Metamorphic (MM) 5%-In Cells 10 runs, 22 wafers, 205 cells

Prototype 3J Metamorphic Prototype 3J Metamorphic Cell Builds Cell Builds

3J MM Cell Efficiency Bin

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SLIDE 27
  • R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

27

cap contact AR

(Al)GaInP Cell 1 1.9 eV

wide-Eg tunnel junction

AlGa(In)As Cell 2 1.6 eV Ga(In)As Cell 3 1.4 eV

tunnel junction AR

Ga(In)As buffer

Ge Cell 4 and substrate 0.67 eV

nucleation back contact

wide-Eg tunnel junction cap contact AR

(Al)GaInP Cell 1 1.9 eV

wide-Eg tunnel junction

AlGa(In)As Cell 2 1.6 eV Ga(In)As Cell 3 1.4 eV

tunnel junction AR

Ga(In)As buffer

Ge Cell 4 and substrate 0.67 eV

nucleation nucleation back contact

wide-Eg tunnel junction

0.05 0.1 0.15 0.2 0.25 1 2 3 4 5

Voltage (V)

Current Density / Incident Intensity (A/W)

MJ cell subcell 1 subcell 2 subcell 3 subcell 4

4 4-

  • Junction

Junction Lattice Lattice-

  • Matched Cell

Matched Cell

  • Current density in spectrum above Ge cell 4 is divided 3 ways among

GaInAs, AlGa(In)As, GaInP cells

  • Lower current and I2R resistive power loss
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SLIDE 28
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10 20 30 40 50 60 70 80 90 100 300 500 700 900 1100 1300 1500 1700 1900 Wavelength (nm) External Quantum Efficiency (%)

200 400 600 800 1000 1200 1400 1600

Intensity Per Unit Wavelength (W/(m2μm))

AlGaInP subcell 1 1.95 eV AlGaInAs subcell 2 1.66 eV GaInAs subcell 3 1.39 eV Ge subcell 4 0.72 eV All subcells AM1.5D ASTM G173-03

Measured 4 Measured 4-

  • Junction Cell

Junction Cell Quantum Efficiency Quantum Efficiency

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Light I Light I-

  • V Curves

V Curves Record Efficiency Cells Record Efficiency Cells

  • Light I-V curves for 3-junction upright MM (40.7%), 3J lattice-matched (41.6%),

3J lattice-matched at 822 suns (39.1%), and 4J lattice-matched cell (36.9%)

0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.16 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Voltage (V) Current Density / Inc. Intensity (A/W) .

Metamorphic Lattice-matched LM, 822 suns 4J Cell 3J Conc. 3J Conc. 3J Conc. 4J Conc. Cell Cell Cell Cell Voc 2.911 3.192 V 3.251 4.398 V Jsc/inten. 0.1596 0.1467 A/W 0.1467 0.0980 A/W Vmp 2.589 2.851 V 2.781 3.950 V FF 0.875 0.887 0.841 0.856

  • conc. 240 364 suns 822 500 suns

area 0.267 0.317 cm

2 0.317 0.208 cm 2

  • Eff. 40.7% 41.6% 40.1% 36.9%

AM1.5D, AM1.5D, AM1.5D, AM1.5D, low -AOD spectrum ASTM G173-03 ASTM G173-03 ASTM G173-03

  • Prelim. meas.

Independently confirmed meas. 25°C 25°C

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The Solar Resource and CPV Economics

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5 6 5 6

  • Entire US electricity demand can be provided by concentrator PV arrays

using 37%-efficient cells on:

  • r ten 50 km x 50 km areas
  • r similar division across US

Ref.: http://rredc.nrel.gov/solar/old_data/ nsrdb/redbook/atlas/

150 km x 150 km area of land

The Solar Resource The Solar Resource

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Map source: http://www.nrel.gov/gis/images/map_csp_us_annual_may2004.jpg CPV cost superiority 40% cell efficiency CPV cost superiority 50% cell efficiency Map source: http://www.nrel.gov/gis/images/map_csp_us_annual_may2004.jpg CPV cost superiority 40% cell efficiency CPV cost superiority 50% cell efficiency

Concentrator Photovoltaic Concentrator Photovoltaic (CPV) Electricity Generation (CPV) Electricity Generation

Higher multijunction cell efficiency has a huge impact on the economics of CPV, and on the way we will generate electricity.

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  • Urgent global need to address carbon emission, climate change, and

energy security concerns → renewable electric power can help

  • Theoretical solar conversion efficiency

– Examining built-in assumptions points out opportunities for higher PV efficiency – Multijunction architectures, up/down conversion, quantum structures, intermediate bands, hot-carrier effects, solar concentration → higher η – Theo. solar cell η > 70%, practical η > 50% achievable

  • Metamorphic multijunction cells have begun to realize their promise

– Metamorphic semiconductors offer vastly expanded of band gaps – 40.7% metamorphic GaInP/ GaInAs/ Ge 3J cells demonstrated – First solar cells of any type to reach over 40% efficiency

  • New world record efficiency of 41.6% demonstrated

– Highest efficiency yet measured for any type of solar cell – 41.6% efficiency independently verified at NREL (364 suns, 25°C, AM1.5D)

  • Solar cells with efficiencies in this range can transform the way we

generate most of our electricity, and make the PV market explode

Summary Summary