Tritiated Amorphous Silicon: Insights into the Staebler-Wronski Mechanism
Hydrogen, though essential for device-quality amorphous silicon, likely contributes to the light-induced degradation process (Staebler-Wronski effect) that reduces the solar cell efficiency by about 4 absolute percent. We are testing the role of hydrogen by using its isotope tritium. When tritium bonded to Si spontaneously decays into inert helium-3, it should leave behind the Si dangling bond defect. We have studied degradation due to tritium and note its resemblance to the Staebler-Wronski effect. Surprisingly, 100x fewer defects are created than expected from the tritium decay rate, suggesting a mechanism that heals most of the defects, even at temperatures down to 4 K. We consider different mechanisms for the thermal and athermal healing processes (e.g. motion of hydrogen, effect of beta-electrons, decay of hydrogen-tritium molecules). Our findings shed new light on the degradation mechanism in a Si:H and help reveal the role of hydrogen and structural rearrangements near a newly created defect.
- Research Organization:
- National Renewable Energy Laboratory (NREL), Golden, CO.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC36-99GO10337
- OSTI ID:
- 860694
- Report Number(s):
- NREL/CP-520-37023
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
14 SOLAR ENERGY
36 MATERIALS SCIENCE
AMORPHOUS SILICON
BETA-ELECTRONS
DECAY
DEFECTS
EFFICIENCY
HEALING
HELIUM 3
HYDROGEN
ISOTOPE TRITIUM
MAGNETIC RESONANCE
PHOTOLUMINESCENCE ABSORPTION SPECTROSCOPY (PLAS)
PHOTOTHERMAL DEFLECTION SPECTROSCOPY (PDS)
PV
SILICON
SOLAR CELLS
SOLAR ENERGY
STAEBLER-WRONSKI EFFECT
Silicon Materials and Devices
Solar Energy - Photovoltaics
TESTING
THIN FILM
TRITIUM