Photovoltaic Cells for Optical Power and Data Transmission

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1 Photovoltaic Cells for Optical Power and Transmission H. Helmers, S.P. Philipps, S.K. Reichmuth, E. Oliva, D. Lackner, A.W. Bett Fraunhofer Institute for Solar Energy Systems ISE European Telemetry and Test Conference etc2014 Nürnberg, June 3,

2 Optical Power Transmission Concept Power Power Laser Hustvedt/CC-BY-SA-3.0/GFDL Optical fiber PV cell 2

3 Optical Power Transmission Concept Power Laser PV cell Power 3

4 Optical Power and Transmission Coupling of a Signal into the Same Fiber Power Laser PV cell Power Laser Photo 4

5 Optical Power and Transmission DC Power + AC Signal DC Power AC Laser PV cell Power 5

6 Optical Power and Transmission Power and Bidirectional by Light Power Laser PV cell Power Laser Photo Photo Laser 6

7 Optical Power and Transmission Power and Bidirectional by Light DC Power AC Laser PV cell Power Photo Laser 7

8 Application Examples Fiber Optic Cable Replaces Copper Wiring Picture: Dennis Richardson Galvanic isolation Picture: www. cleanandgreenlaw.com Lightning protection Picture: mysite.du.edu/ ~lconyers/serdp/figure5.htm Electromagnetic interference 8 Picture: Shutterstock Avoidance of sparks and short circuits Picture: wiki.vag.cc Weight reduction Picture: Uni Heidelberg High magnetic fields

9 Laser Power Converter (LPC) Requirements for the Photovoltaic Cell Adjustment for laser wavelength High efficiency High power density High voltage output Combination with data transmission 9

10 Laser Power Converter (LPC) Requirements for the Photovoltaic Cell Adjustment for laser wavelength High efficiency High power density High voltage output Combination with data transmission 10

11 Conversion of Light into Electrical Power The Semiconductor Bandgap 11 Source: after Bubenzer, Luther, Photovoltaic Guidebook for Decisionmakers

Adjustment for Laser Wavelength III-V Compound Semiconductors III IV V 5 B 6 C 7 N 13 Al 14 Si 15 P 31 Ga 32 Ge 33 As 49 In 50 Sn 51 Sb 81 Tl 82 Pb 83 Bi Bandgap [ev] 2.5 AlP 2.0 1.5 1.0 0.5 GaP Ga 0.

12 Adjustment for Laser Wavelength III-V Compound Semiconductors III IV V 5 B 6 C 7 N 13 Al 14 Si 15 P 31 Ga 32 Ge 33 As 49 In 50 Sn 51 Sb 81 Tl 82 Pb 83 Bi Bandgap [ev] 2.5 AlP GaP Ga 0.50 In 0.50 P GaAs Si AlAs AlSb InP Ga 0.16 In 0.84 P 0.69 As 0.31 Ge GaSb Ga 0.47 In 0.53 As InAs InSb Lattice constant [Å] Wavelength [µm] Material composition determines the bandgap! 12

13 Adjustment for Laser Wavelength External Quantum Efficiencies of Different Materials Ga 0.50 In 0.50 P λ c =670 nm GaAs λ c =870 nm Ga 0.16 In 0.84 P 0.69 As 0.31 λ c =1100 nm Ga 0.47 In 0.53 As λ c =1680 nm Laser wavelengths External quantum efficiency [1] Ga0.50In0.50P GaAs Ga0.16In0.84P0.69As0.31 Ga0.47In0.53As 650 nm 850 nm 808 nm 980 nm 1064 nm 1310 nm 1550 nm Wavelength [nm] 13

14 Laser Power Converter (LPC) Requirements for the Photovoltaic Cell Adjustment for laser wavelength High efficiency High power density High voltage output Combination with data transmission 14

15 High Efficiency Ultimate Photon Management for Monochromatic Light Conversion Matching of bandgap and laser wavelength No thermalization losses No transmission losses Ideal efficiency (in the radiative limit) >80% Monochromatic efficiency [%] Bandgap [ev] GaAs Detailed balance calculation Irradiance [W/cm 2 ] Wavelength [nm] Bett et al., Proc. 33rd IEEE PVSC,

16 High Efficiency GaAs Converter for 810 nm Single-junction GaAs 1 mm 175 Current [ma] P in = nm η = 54.9% J SC = 18.8 A/cm² V OC = V FF = 0.88 A = 0.89 mm² T = 25 C Voltage [V] Oliva et al., Prog. Photovolt. Res. Appl. 16(4),

17 Laser Power Converter (LPC) Requirements for the Photovoltaic Cell Adjustment for laser wavelength High efficiency High power density High voltage output Combination with data transmission 17

18 High Power Density Challenge Cell size: 0.01 cm² Laser power: 1 W 100 W/cm² High power density High current density Series resistance losses Emitter Base Substrate Symmetry element 18

19 High Power Density Optimized Front Grid Metallization Low series resistance Low-loss current flow Low shading Preservation of active area 19

Improved series resistance Material with higher bandgap

20 High Power Density Transparent Lateral Conduction Layer Lateral conduction layer Highly doped High conductivity Improved series resistance Material with higher bandgap Transparent for the monochromatic laser light Cond. layer Emitter Base Substrate 20

21 Laser Power Converter (LPC) Requirements for the Photovoltaic Cell Adjustment for laser wavelength High efficiency High power density High voltage output Combination with data transmission 21

by tunnel s Division of the current Multiplication of the

22 High Voltage Vertical Interconnection (Multi-Junction) Multi-junction cell Vertical stack Serial interconnection by tunnel s Division of the current Multiplication of the voltage Cond. layer Cond. PV cell Tunnel layer PV cell Substrate 22

23 High Voltage Dual-Junction GaAs/GaAs Cell Dual-junction cell Vertical stack of two GaAs cells Serial interconnection by tunnel s Half the current Twice the voltage Open circuit voltage [V] Laser irradiation: 810 nm Irradiance [W/cm²] Schubert et al., IEEE Trans. Electron Devices 56(2),

24 High Voltage Lateral Interconnection ( MIM ) Segmentation of the cell area Additional lateral conduction layer on the back Trenches for separation of individual segments Serial interconnection on the front Monolithic interconnected module (MIM) concept Cond. layer Cond. layer PV cell PV cell Cond. layer Cond. layer Semi-insulating substrate 24

25 High Voltage 6-Segment GaAs MIM Cell Segmentation of the cell area Additional lateral conduction layer on the back Trenches for separation of individual segments Serial interconnection on the front Monolithic interconnected module (MIM) concept 25

26 High Voltage 6-Segment GaAs MIM Cell Power [mw] A=3.39 mm² Irradiance Voltage [V] 26

27 Laser Power Converter (LPC) Requirements for the Photovoltaic Cell Adjustment for laser wavelength High efficiency High power density High voltage output Combination with data transmission 27

28 Optical Power and Transmission Uplink: DC Power + AC Signal Downlink: Separate Fiber DC Power AC Laser PV cell Power Photo Laser 28

cells P el =3 W Integrated DC/DC conversion: output voltages +18 V, -10 V, +3.

29 Application Example 1 Power Supply in High-Voltage Environment Power supply for inverter in power plant High-voltage environment: galvanic isolation from ground 6 PV cells P el =3 W Integrated DC/DC conversion: output voltages +18 V, -10 V, +3.3 V Fiber link High voltage: 10 kv IGBT module PV cell DC/DC converter Gate driver Laser μc, laser driver 29

30 Optical Power and Transmission Power and Bidirectional by Light Power Laser PV cell Power Laser Photo Photo Laser 30

31 Application Example 2 Structural Health Monitoring with Lightning Protection WLAN access point acquisition unit Base station Sensor unit Vibration sensors 31

32 Structural Health Monitoring in Wind Turbines Performance Demonstrator system in a 1.5 MW wind turbine Extended 5 months field trial Acceleration [g] 17. ITG/GMA Fachtagung Sensoren und Messsysteme 2014 Presentation by Kai Worms Wed., June 4, 15h40 NCC West, Room London (Level 2) Acceleration [g] Time [s] Worms et al., Proc. 17. ITG/GMA Fachtagung Sensoren und Messsysteme, Time [s]

33 Summary PV Cells for Optical Power and Transmission Laser power converters from different III-V materials Optimization for different laser wavelengths Concepts for increased voltage output Combination of power and data transmission Reliable operation in harsh environments 33

Rexroth the Federal Ministry for Economic Affairs and Energy (BMWi) for funding of the Optowind project (contract number

34 Acknowledgements Thanks to all members of the III-V Epitaxy and Solar Cells group and Patrick Blattert, David Derix, and Dirk Kranzer from the Power Electronics group at Fraunhofer ISE our partners at the Karlsruhe Institute of Technology and at Bosch Rexroth the Federal Ministry for Economic Affairs and Energy (BMWi) for funding of the Optowind project (contract number B) the European Union s Seventh Framework Programme for research, technological development and demonstration for funding 34

35 Thank you for your attention! Fraunhofer Institute for Solar Energy Systems ISE Dr. Henning Helmers 35

Thin film PV Technologies III- V PV Technology

Thin film PV Technologies III- V PV Technology Week 5.1 Arno Smets ` (Source: NASA) III V PV Technology Semiconductor Materials III- V semiconductors: GaAs: GaP: InP: InAs: GaInAs: GaInP: AlGaInAs: AlGaInP: