Materials Optimization for Silicon Heterojunction Solar Cells Using Spectroscopic Ellipsometry
We have used hot wire chemical vapor deposition (HWCVD) to fabricate silicon heterojunction (SHJ) solar cells on p-type FZ silicon substrates with efficiencies as high as 18.2%. The best cells are deposited on anisotropically-textured (100) silicon substrates where an etching process creates pyramidal facets with (111) crystal faces. Texturing increases J{sub sc} through enhanced light trapping, yet our highest V{sub oc} devices are deposited on un-textured (100) substrates. One of the key factors in maximizing the efficiency of our SHJ devices is the process of optimization of the material properties of the 3-5 nm thick hydrogenated amorphous silicon (a-Si:H) layers used to create the junction and back contact in these cells. Such optimization is technically challenging because of the difficulty in measuring the properties of extremely thin layers. In this study, we have utilized spectroscopic ellipsometry (SE) and photoconductivity decay to conclude that a-Si:H films grown on (111) substrates are substantially similar to films grown on (100) substrates. In addition, analysis of the substrate temperature dependence of surface roughness evolution reveals a substrate-independent mechanism of surface smoothening with an activation energy of 0.28 eV. Analysis of the substrate temperature dependence of surface passivation reveals a passivation mechanism with an activation energy of 0.63 eV.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC36-08GO28308
- OSTI ID:
- 978495
- Resource Relation:
- Conference: Amorphous and Polycrystalline Thin-Film Silicon Science and Technology - 2007: Proceedings of the Materials Research Society Symposium, 9-13 April 2007, San Francisco, California; Materials Research Society Symposium Proceedings, Vol. 989; Related Information: Paper No. 0989-A24-04
- Country of Publication:
- United States
- Language:
- English
Similar Records
High Open-Circuit Voltage in Silicon Heterojunction Solar Cells
Progress in Silicon Heterojunction Devices by Hot-Wire CVD: Preprint
Related Subjects
36 MATERIALS SCIENCE
ACTIVATION ENERGY
CHEMICAL VAPOR DEPOSITION
DECAY
EFFICIENCY
ELLIPSOMETRY
ETCHING
HETEROJUNCTIONS
OPTIMIZATION
PASSIVATION
PHOTOCONDUCTIVITY
ROUGHNESS
SILICON
SOLAR CELLS
SUBSTRATES
TEMPERATURE DEPENDENCE
TRAPPING
Solar Energy - Photovoltaics
Silicon Materials and Devices