Microstructural defects of device quality hot-wire CVD poly-silicon films
Two types of poly-Si:H thin films made by Hot Wire CVD have been evaluated with respect to utilization in solar cells. Poly-Si:H films made at high hydrogen dilution are highly porous and have large interconnected voids. The void density is 25,000/{micro}m{sup 3} as determined by XTEM. On the other hand, poly-Si:H layers made at low hydrogen dilution have a compact structure and a much smaller density of voids. In these films, two types of voids exist: globular voids smaller than 15 nm, and elongated voids, often located between columns of large crystals of 150--250 nm wide at the top. The density for the 5--15 nm spherical voids is usually {approximately} 50/{micro}m{sup 3}, but larger concentrations often occur locally, up to 1,000/{micro}m{sup 3}, i.e., 0.05% volume fraction. high oxygen content in the poly-Si films made at high hydrogen dilution is largely due to post deposition intrusion of water vapor through the interconnected voids. profiled layers are made by depositing device quality poly-Si:H layers (low hydrogen dilution) on top of a seed layer (high hydrogen dilution) of high nucleation density. Cells incorporating profiled poly-Si:H films as i-layers at a deposition rate of 0.5 nm/s were made on stainless steel substrates in the configuration SS/n-{micro}c-Si:H(PECVD)/i-poly-Si:H(HWCVD)/p-{micro}c-Si:H(PECVD)/ITO. For the n-i-p solar cell with poly-Si i-layer they obtained an efficiency of 4.41% and a FF of 0.607. Due to native surface texture a current density of 19.95 mA/cm{sup 2} is generated in only {approximately} 1.22 {micro}m thick i-layer without back reflector.
- Research Organization:
- Utrecht Univ. (NL)
- Sponsoring Organization:
- Netherlands Organisation for Energy and Environment
- OSTI ID:
- 20107955
- Resource Relation:
- Conference: 1999 Materials Research Society Spring Meeting, San Francisco, CA (US), 04/05/1999--04/09/1999; Other Information: PBD: 1999; Related Information: In: Amorphous and heterogeneous silicon thin films: Fundamentals to devices -- 1999. Materials Research Society symposium proceedings: Volume 557, by Branz, H.M.; Collins, R.W.; Okamoto, Hiroaki; Guha, S.; Schropp, R. [eds.], 908 pages.
- Country of Publication:
- United States
- Language:
- English
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