Microscopic Mechanism of the Staebler-Wronski Effect in a-Si Films and High-Efficiency Solar Cells: Final Subcontract Report, 1 October 2001--30 September 2004
In high growth rate ({ge} 50 {angstrom}/s) HW-CVD a-Si:H films, for the first time, we show gaseous molecules in nanovoids ({approx}2% volume fraction of tube-like nanoscale voids), and demonstrate that confinement on the nanometer scale generates NMR effects that have never been observed in macroscopic systems. In the same system we found the PL peak red shift. We suggest that highly strained bonds on the inner surfaces of the nanoscale voids form broad conduction-band tail states that are responsible for the PL red shift. We characterized the structural transition from a- to nc-Si as function of H-dilution, thickness and T{sub s} of both HW- and PE-CVD films using IR, Raman, PL, CPM/PDS and E{sub a} et al. We found not only the c-Si volume fraction but also the g.b. and microstructures play an important role in the properties of the i-layer and their solar cell performance. We found a narrow structural transition zone in which the bond-angle variation, {Delta}{Theta}, decreases from 10{sup o} to 8{sup o}. For nc-Si samples, we found a characteristic low energy PL peak and proved that is originated from the g.b. regions. Using micro-Raman, we found the structural non-uniformity in the mixed-phase solar cells that showed V{sub oc} enhancement after light soaking. Using micro-Raman, we also found the slight increase of crystallinity in M/{mu}c-Si/M devices after current forming.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC36-99-GO10337
- OSTI ID:
- 15016380
- Report Number(s):
- NREL/SR-520-37990; ADJ-1-30630-09; TRN: US200513%%351
- Resource Relation:
- Other Information: PBD: 1 May 2005; Related Information: Work performed by University of North Carolina, Chapel Hill, North Carolina
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
BOND ANGLE
CONFINEMENT
PERFORMANCE
RED SHIFT
SOLAR CELLS
THICKNESS
PV
STAEBLER-WRONSKI EFFECT
AMORPHOUS SILICON (A-SI:H)
MICROSCOPIC MECHANISM
PHOTOLUMINESCENCE (PL)
RAMAN SPECTROSCOPIES
MANUFACTURER
THIN FILM
LIGHT-INDUCED DEGRADATION
SOLAR ENERGY - PHOTOVOLTAICS