Recombination and Metastability in Amorphous Silicon and Silicon Germanium Alloys: Annual Subcontract Report, 1 February 1992 - 31 January 1993
This report describes work during the second year of a continuing research study. The work is designed to help us understand how recombination, trapping, and band-mobility modification affecting the electronic properties of amorphous semiconductors can be measured, characterized, and described by an appropriate spectrum of defect states. We also worked to determine how light-induced defects in a Si:H and native defects in a-Si:H and native defects in a-Si:H and native defects in a SiGe:H affect transport properties in these materials. During this second year, we continued our experiments on electroluminescence (EL) and transient forward bias current, as well as photocurrent before and after light soaking. We started a program to study thin (0.4{mu}m) p-i-n solar cells, and we studied the effect of optical bias on charge transport in a Si:H films. We performed analytical calculations on a model that predicts an exponential energy region for band tails from dilute random charges. We developed a model for the carrier-recombination-lifetime distribution. We solved the equations for H-diffusion including deep trap levels. Lastly, we analyzed simulation data under forward bias in p-i-n devices. The most interesting and important results were obtained on the EL spectra in thin solar cell devices. We found that, at elevated temperatures, thin p-i-n devices displayed primarily defect luminescence (0.8-0.9 eV), while in thick (> 2 {mu}m) devices the luminescence observed was the main band (l.l-1.2 eV). We also found that, in thin cells with buffered layers, p-b-i-n`s the main band luminescence was more pronounced than that in simple p-i-n`s. For the first time we have distinguished between bulk and junction- controlled recombination.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE)
- DOE Contract Number:
- AC36-08GO28308
- OSTI ID:
- 10106395
- Report Number(s):
- NREL/TP-451-5834; ON: DE94000237; BR: WM1020000
- Resource Relation:
- Other Information: PBD: Nov 1993
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SILICON ALLOYS
ELECTRICAL PROPERTIES
GERMANIUM ALLOYS
SILICON SOLAR CELLS
MATERIALS
PROGRESS REPORT
AMORPHOUS STATE
INTERMETALLIC COMPOUNDS
ELECTROLUMINESCENCE
CHARGE CARRIERS
photovoltaics
solar cells
amorphous silicon
silicon germanium
alloys
140501
360606
360602
PHOTOVOLTAIC CONVERSION
PHYSICAL PROPERTIES
STRUCTURE AND PHASE STUDIES