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Articles you may be interested inHydrogenated amorphous silicon oxide containing a microcrystalline silicon phase and usage as an intermediate reflector in thin-film silicon solar cells Deposition of microcrystalline silicon prepared by hot-wire chemical-vapor deposition: The influence of the deposition parameters on the material properties and solar cell performance J. Appl. Phys. 98, 024905 (2005); 10.1063/1.1957128 Role of growth temperature and the presence of dopants in layer-by-layer plasma deposition of thin microcrystalline silicon (μc-Si:H) doped layersThe influence of atmospheric contaminants oxygen and nitrogen on the performance of thin-film hydrogenated amorphous silicon ͑a-Si: H͒ solar cells grown by plasma-enhanced chemical vapor deposition at 13.56 MHz was systematically investigated. The question is addressed as to what degree of high base pressures ͑up to 10 −4 Torr͒ are compatible with the preparation of good quality amorphous silicon based solar cells. The data show that for the intrinsic a-Si: H absorber layer exists critical oxygen and nitrogen contamination levels ͑about 2 ϫ 10 19 atoms/ cm 3 and 4 ϫ 10 18 atoms/ cm 3 , respectively͒. These levels define the minimum impurity concentration that causes a deterioration in solar cell performance. This critical concentration is found to depend little on the applied deposition regime. By enhancing, for example, the flow of process gases, a higher base pressure ͑and leak rate͒ can be tolerated before reaching the critical contamination level. The electrical properties of the corresponding films show that increasing oxygen and nitrogen contamination results in an increase in dark conductivity and photoconductivity, while activation energy and photosensitivity are decreased. These effects are attributed to nitrogen and oxygen induced donor states, which cause a shift of the Fermi level toward the conduction band and presumably deteriorate the built-in electric field in the solar cells. Higher doping efficiencies are observed for nitrogen compared to oxygen. Alloying effects ͑formation of SiO x ͒ are observed for oxygen contaminations above 10 20 atoms/ cm 3 , leading to an increase in the band gap.

A theoretical treatment of the deposition process in a non-reactive high power pulsed magnetron sputtering discharge is presented. This leads to the development of a semi-quantitative model that describes the deposition rate as a function of process parameters, such as the target voltage, the peak target current density, the pulse frequency and the pulse duty cycle. The effect of these parameters on the deposition rate is studied experimentally using carbon, chromium and copper targets. The implementation of the model on the experimental results enables the estimation of the relative fractions of the sputtering gas ions (Ar+) and the sputtered metal ions (M+) in the total ion flux at the target. The M+ content in the target ion current is calculated to adopt values up to ∼72% and ∼98% for the chromium and the copper targets, respectively. In contrast, the target ion current is found to consist mostly of Ar+ species in the case of the carbon target. The significantly higher fractions of M+ ions for chromium and copper are attributed to their higher ionization probability and their higher sputtering yield in comparison with carbon.

Hydrogenated amorphous silicon (a-Si:H) is conventionally deposited using static plasma-enhanced chemical vapor deposition (PECVD) processes. In this work, a very high frequency (VHF) dynamic deposition technique is presented, on the basis of linear plasma sources. This configuration deploys a simple reactor design and enables continuous deposition processes, leading to a high throughput. Hence, this technique may facilitate the use of flexible substrates. As a result, the production costs of thin-film silicon solar cells could be reduced significantly.We found a suitable regime for the homogeneous deposition of a-Si:H layers for growth rates from 0.35-1.1 nm/s. The single layer properties as well as the performance of corresponding a-Si:H solar cells are investigated and compared with a state-of-the-art radio frequency (RF) PECVD regime. By analyzing the Fourier transform infrared spectroscopy spectra of single layers, we found an increasing hydrogen concentration with deposition rate for both techniques, which is in agreement with earlier findings. At a given growth rate, the hydrogen concentration was at the same level for intrinsic layers deposited by RF-PECVD and VHF-PECVD.The initial efficiency of the corresponding p-i-n solar cells ranged from 9.6% at a deposition rate of 0.2 nm/s (RF regime) to 8.9% at 1.1 nm/s (VHF regime). After degradation, the solar cell efficiency stabilized between 7.8% and 5.9%, respectively. The solar cells incorporating intrinsic layers grown dynamically using the linear plasma sources and very high frequencies showed a higher stabilized efficiency and lower degradation loss than solar cells with intrinsic layers grown statically by RF-PECVD at the same deposition rate.

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