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High-Efficiency GaAs Thin-Film Solar Cell Reliability · High-Efficiency GaAs Thin-Film Solar Cell...
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Confidential and Proprietary Information of ALTA Devices, Inc. High-Efficiency GaAs Thin-Film Solar Cell Reliability NREL PV Module Reliability Workshop, Feb. 26-27, 2013 Erhong Li and Prasad Chaparala Alta Devices, Inc.
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Confidential and Proprietary Information of ALTA Devices, Inc.
High-Efficiency GaAs Thin-Film Solar Cell Reliability NREL PV Module Reliability Workshop, Feb. 26-27, 2013
Erhong Li and Prasad Chaparala
Alta Devices, Inc.
Confidential and Proprietary Information of ALTA Devices, Inc.
Alta Devices Flexible Solar Technology
‣ World-record efficiencies • Single junction cell/module: 28.8% / 24.1% • Dual junction cell: 30.8%
HIGH ENERGY DENSITY 240W/m2
HIGHLY FLEXIBLE <15cm RADIUS
ULTRA LIGHT WEIGHT 1 gm/W
CAN BE MADE INTO ANY FORM FACTOR
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How Alta’s Flexible Cells Are Formed
Substrate Reuse
MOCVD
Lift-off Epitaxial
Front metal AR CoatingCut Test
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Mobile Power Applications
UAVs / Aerospace
Remote Power
Portable Electronics
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Built-in Reliability Methodology
‣ In-depth reliability characterization, beyond certification & specs • Know when, where and why it fails
‣ Built-in reliability mindset • Reliability - integral part of development • Cell-level accelerated testing for fast feed-back
System Reliability
Module Reliability
Interconnect Reliability
Cell Reliability
IEC tests Lifetime estimation Failure limits
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Reliability Tests
‣ Technology Reliability Characterization • Accelerated tests on bare solar cells (un-encapsulated) • IEC tests on glass mini-modules (150 cm2)
‣ Reliability Tests Sample HTOL LTSL Damp Heat Thermal
Cycling Humidity
Freeze Cells 150C
168hrs -60C
168hrs 85C/85%RH
168hrs -40C/85C 200 cys
NA
Modules 110C NA IEC61646 IEC61646 IEC61646 1000hrs
‣ Failure Criterion • Pmax Degradation(%) = (Pmax@Tx-Pmax@T0)/Pmax@T0*100
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Cell Level Reliability – High Temperature Test
‣ Cells tested @150C for 168hrs ‣ Pmax degradation < 6%
PL @0hr
PL @168hrs
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Cell Level Reliability – Low Temperature Test
‣ Cells tested @-60C for 168hrs
‣ Pmax degradation < 2%
PL @0hr
PL @168hrs
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Cell Level Reliability - Damp Heat Test
‣ Cells tested @ 85C/85%RH for 168hrs ‣ Pmax degradation < 6%
PL @0hr
PL @168hrs
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Cell Level Reliability - Thermal Cycling Test
‣ Thermal cycling under 2” bend radius (-40C/85C, IEC profile, 200 cycles) ‣ Pmax degradation < 10%
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11 Erhong Li, NREL PVMRW 2013
Reliability of Cells from Multiple Substrate Reuses
‣ Substrate reuse is one of the key process steps to lower cost for GaAs thin-film solar technology ‣ Cells tested @150C for 168hrs ‣ No intrinsic degradation mechanism was found on
material up to 10-time substrate reuse
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Module Level Reliability – High Temperature Test
‣ Module tested @110C, 1000hrs
‣ Pmax degradation < 5%
Target
PL @0hr
PL @4000hrs
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Module Level Reliability – Damp Heat Test
‣ Pmax degradation < 5% at 1000hrs ‣ Results exceed IEC test requirements
Target
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Module Level Reliability – Thermal Cycling Test
‣ Pmax degradation < 5% at 200cys ‣ Results exceed IEC test requirements
Target
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Module Level Reliability – Humidity Freeze Test
‣ Pmax degradation < 5% at 10cys ‣ Results exceed IEC test requirements
Target
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Module Level Reliability – UV + TC + HF EL @0hr ‣ Pmax degradation < 5%
‣ Modules passed UV sequence test • UV (15kWh/m2) • TC50 • HF10
EL @UV+TC50+HF10
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Conclusion
‣ Thin-film solar cells from GaAs reuse substrate show no intrinsic degradation after reliability tests
‣ Broad range of cell-level and module-level reliability tests demonstrate that Alta Devices GaAs thin-film solar technology from Epitaxial Lift-off (ELO) process exceeds lifetime requirements for PV applications
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Acknowledgement
‣ Thanks to Chris Ling, Sharon Myers and Chris France for support
‣ Thanks to the Device/EPI/Process/Integration/Matrix team to provide materials for this reliability study
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