Band-Gap-Engineered Architectures for High-Efficiency Multijunction - PowerPoint PPT Presentation

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

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

Outline Outline contact contact AR AR • Solar cell theoretical efficiency limits n + -GaInAs n + -GaInAs n-AlInP window n-AlInP window Top Cell Top Cell n-GaInP emitter n-GaInP emitter p-GaInP base p-GaInP base Wide-Eg Tunnel Wide-Eg Tunnel – Opportunities to change ground rules for higher terrestrial efficiency p-AlGaInP BSF p-AlGaInP BSF p ++ -TJ p ++ -TJ n ++ -TJ n ++ -TJ Middle Cell Middle Cell n-GaInP window n-GaInP window – Cell architectures capable of >70% in theory, >50% in practice n-GaInAs emitter n-GaInAs emitter p-GaInAs base p-GaInAs base p-GaInP BSF p-GaInP BSF p-GaInAs p-GaInAs Tunnel Junction Tunnel Junction step-graded step-graded • Metamorphic semiconductor materials buffer buffer p ++ -TJ p ++ -TJ Bottom Cell Bottom Cell n ++ -TJ n ++ -TJ nucleation nucleation n + -Ge emitter n + -Ge emitter – Control of band gap to tune to solar spectrum p-Ge base p-Ge base and substrate and substrate contact contact • High-efficiency terrestrial concentrator cells metal gridline semi- conductor bonded – Metamorphic (MM) and lattice-matched (LM) 3-junction interface 2.0-eV AlGaInP cell 1 1.7-eV AlGaInAs cell 2 solar cells with > 40% efficiency 1.4-eV GaInAs cell 3 – 4-junction MM and LM concentrator cells 1.1-eV GaInPAs cell 4 – Inverted metamorphic structure, semiconductor 0.75-eV GaInAs cell 5 bonded technology (SBT) for MJ terrestrial concentrator cells • The solar resource and concentrator photovoltaic (CPV) system economics 3 R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

High-Efficiency Multijunction Cell Architectures 4 R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

Maximum Solar Cell Maximum Solar Cell Efficiencies Efficiencies Measured Theoretical References C. H. Henry, “Limiting efficiencies of ideal single and multiple energy gap terrestrial T = 300 K, T sun ≈ 5800 K 95% Carnot eff. = 1 – T/T sun solar cells,” J. Appl. Phys. , 51 , 4494 (1980). 93% W. Shockley and H. J. Queisser, “Detailed Balance Limit of Efficiency of p-n Junction Max. eff. of solar energy conversion Solar Cells,” J. Appl. Phys. , 32 , 510 (1961). = 1 – TS/E = 1 – (4/3)T/T sun (Henry) 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. 72% Ideal 36-gap solar cell at 1000 suns (Henry) 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. 56% Ideal 3-gap solar cell at 1000 suns (Henry) R. P. Gale et al. , "High-Efficiency GaAs/CuInSe 2 and AlGaAs/CuInSe 2 Thin-Film 50% Tandem Solar Cells," Proc. 21st IEEE Photovoltaic Specialists Conf. , Kissimmee, Ideal 2-gap solar cell at 1000 suns (Henry) 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). 44% Ultimate eff. of device with cutoff E g : (Shockley, Queisser) 43% 1-gap cell at 1 sun with carrier multiplication 3-gap GaInP/GaInAs/Ge LM cell, 364 suns (Spectrolab) 41.6% (>1 e-h pair per photon) (Werner, Kolodinski, Queisser) 3-gap GaInP/GaInAs/Ge MM cell, 240 suns (Spectrolab) 40.7% 37% Ideal 1-gap solar cell at 1000 suns (Henry) 3-gap GaInP/GaAs/GaInAs cell at 1 sun (NREL) 33.8% 31% Ideal 1-gap solar cell at 1 sun (Henry) 30% Detailed balance limit of 1 gap solar cell at 1 sun 1-gap solar cell (silicon, 1.12 eV) at 92 suns (Amonix) 27.6% (Shockley, Queisser) 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% 5 R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

Metamorphic (MM) Metamorphic (MM) 3- -Junction Solar Cell Junction Solar Cell 3 contact contact 0.3 AR AR Current Density / Incident Intensity (A/W) n + -GaInAs n + -GaInAs MJ cell n-AlInP window n-AlInP window Top Cell Top Cell n-GaInP emitter n-GaInP emitter 0.25 subcell 1 p-GaInP base p-GaInP base l l e e n n subcell 2 n n u u T T g g E E 0.2 p-AlGaInP BSF p-AlGaInP BSF - - e e d d subcell 3 i i W W p ++ -TJ p ++ -TJ n ++ -TJ n ++ -TJ Middle Cell Middle Cell n-GaInP window n-GaInP window n-GaInAs emitter n-GaInAs emitter 0.15 p-GaInAs base p-GaInAs base p-GaInP BSF p-GaInP BSF 0.1 p-GaInAs p-GaInAs Tunnel Junction Tunnel Junction step-graded step-graded buffer buffer 0.05 p ++ -TJ p ++ -TJ l l l l e e n ++ -TJ n ++ -TJ C C nucleation nucleation m m o o n + -Ge emitter n + -Ge emitter t t t t o o B B p-Ge base p-Ge base 0 and substrate and substrate 0 0.5 1 1.5 2 2.5 3 3.5 contact contact Voltage (V) Lattice-Mismatched or Metamorphic (MM) • Metamorphic growth of upper two subcells, GaInAs and GaInP 6 R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

External QE of LM and MM External QE of LM and MM 3- -Junction Cells Junction Cells 3 100 100 AM1.5D, low-AOD AM1.5G, ASTM G173-03 90 90 AM0, ASTM E490-00a EQE, lattice-matched External Quantum Efficiency (%) 80 EQE, metamorphic 80 Wavelength (mA/(cm 2 μ m)) Current Density per Unit 70 70 60 60 50 50 40 40 30 30 20 20 10 10 0 0 300 500 700 900 1100 1300 1500 1700 1900 Wavelength (nm) 7 R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

Metamorphic (MM) Metamorphic (MM) 3- -Junction Solar Cell Junction Solar Cell 3 3-junction E g1 / E g2 / 0.67 eV cell efficiency 2.1 E g1 = Subcell 1 (Top) Bandgap (eV) . 240 suns (24.0 W/cm 2 ), AM1.5D (ASTM G173-03), 25 o C Ideal efficiency -- radiative recombination limit 2 LM MM 1.9 40.7% 40.1% 1.8 54% 1.7 52% 1.6 50% 48% 1.5 46% 44% 1.4 42% 40% 38% 1.3 1.0 1.1 1.2 1.3 1.4 1.5 1.6 E g2 = Subcell 2 Bandgap (eV) Disordered GaInP top subcell Ordered GaInP top subcell • Metamorphic GaInAs and GaInP subcells bring band gap combination closer to theoretical optimum 8 R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

40.7% - Record 40.7% -Efficient Efficient Record Concentrator Solar Cell Concentrator Solar Cell Spectrolab • First solar cell of Metamorphic any type to reach GaInP/ GaInAs/ Ge Cell over 40% efficiency V oc = 2.911 V 3.832 A/cm 2 J sc = FF = 87.50% V mp = 2.589 V Efficiency = 40.7% ± 2.4% 240 suns (24.0 W/cm 2 ) intensity 0.2669 cm 2 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. Concentrator cell light I-V and efficiency independently verified by J. Kiehl, T. Moriarty, K. Emery – NREL 9 R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009

Metamorphic (MM) 3- -Junction Cells Junction Cells Metamorphic (MM) 3 –– Inverted 1.0 Inverted 1.0- -eV GaInAs Subcell eV GaInAs Subcell –– Ge or GaAs substrate Growth Direction Ge or GaAs substrate cap cap 1.9 eV (Al)GaInP subcell 1 1.4 eV GaInAs subcell 2 graded MM buffer layers 1.0 eV GaInAs subcell 3 Growth on Ge or GaAs substrate, followed by substrate removal from sunward surface 10 R. R. King et al., 24th European Photovoltaic Solar Energy Conf., Hamburg, Germany, Sep. 21-25, 2009