Université de Neuchâtel

Photovoltaic Technology : The Case for Thin-Film Solar Cells

Shah, Arvind ; Torres, Pedro ; Tscharner, Reto ; Wyrsch, Nicolas ; Keppner, Herbert

In: Science, 1999, vol. 285, no. 5428, p. 692-698

The advantages and limitations of photovoltaic solar modules for energy generation are reviewed with their operation principles and physical efficiency limits. Although the main materials currently used or investigated and the associated fabrication technologies are individually described, emphasis is on silicon-based solar cells. Wafer-based crystalline silicon solar modules dominate in terms of...

Université de Neuchâtel

Amorphous silicon solar cells with graded low-level doped i-layerscharacterised by bifacial measurements

Fischer, Diego ; Wyrsch, Nicolas ; Fortmann, C.M. ; Shah, Arvind

In: Conference Record of the 23th IEEE Photovoltaic Specialists Conference, 1993, p. 878-884

Bifacial spectral response characterization of solar cells under near operating condition illumination is used in conjuncture with a novel bifacial DICE analysis to establish the collection efficiency as a function of i-layer position in p-i-n amorphous silicon solar cells. A significant portion of solar cell degradation can be explained in terms of electric field distortions which increase...

Université de Neuchâtel

a-Si:H films deposited at high rates in a 'VHF' silane plasma: potential for low-cost solar cells

Shah, Arvind ; Sauvain, E. ; Wyrsch, Nicolas ; Curtins, H. ; Leutz, B. ; Shen, D. S. ; Chu, V. ; Wagner, S. ; Schade, H. ; Chao, H. W. A.

In: Conference Record of the Twentieth IEEE Photovoltaic Specialists Conference, 1988, vol. 1, p. 282-287

The very-high-frequency glow discharge (VHF-GD) is a high-rate deposition method for amorphous silicon based on the use of plasma excitation frequencies in the range 30-150 MHz. Thereby the high-energy tail of the electron energy density function is enhanced, increasing the deposition rate R, without a corresponding increase in electric field and ion bombardment. Here, an extensive set of...

Université de Neuchâtel

High-rate deposition of hydrogenated amorphous silicon by the VHF-GD method

Curtins, H. ; Favre, M. ; Wyrsch, Nicolas ; Brechet M. ; Prasad K. ; Shah, Arvind

In: Proceedings of the 19th IEEE Photovoltaic Specialists Conference, 1987, p. 695-698

Université de Neuchâtel

Determination of the quality of a-Si:H films: “true”transport parameters

Beck, N. ; Shah, Arvind ; Wyrsch, Nicolas

In: Conference Record of the Twenty Fourth IEEE Photovoltaic Specialists Conference (1994 IEEE First World Conference on Photovoltaic Energy Conversion), 1994, vol. 1, p. 476-479

For the characterisation of a-Si:H layers, steady-state photoconductivity (SSPC) and steady-state photocarrier grating (SSPG) are currently used. But the μτ-products deduced from these measurements are a function of the prevailing dangling bond occupation in the film and, thus, are not a measure of material quality. In the present paper the authors introduce the product...

Université de Neuchâtel

Ultra-Light Amorphous Silicon Cell for Space Applications

Wyrsch, Nicolas ; Dominé, Didier ; Freitas, F. ; Feitknecht, Luc ; Bailat, Julien ; Ballif, Christophe ; Poe, G. ; Bates, K. ; Reed, K.

In: Conference Record of the 2006 IEEE 4th World Conference on Photovoltaic Energy Conversion, 2006, vol. 2, p. 1785-1788

For space applications, solar cells should be optimized for highest power density rather than for highest efficiency. In this context, relatively low efficiency thin-film solar cell may well surpass multi-junction III-V based solar cells if they can be made thin enough. In thin-film solar cells the power density is mostly limited by the substrate. The introduction of ultra-thin polymeric...

Université de Neuchâtel

Correlation between transport properties of a-Si:H layers and cell performances incorporating these layers

Wyrsch, Nicolas ; Beck, N. ; Hof, Ch. ; Goerlitzer, M. ; Shah, Arvind

In: Journal of Non-Crystalline Solids, 1996, vol. 198-200, p. 238-241

Using the new ‘quality parameter’, μ0τ0, the authors were able to show, for the first time, a clear correlation between transport properties of a series of a-Si:H films (grown at various deposition temperatures) and the efficiency of p-i-n cells incorporating the same material as i-layer. In this paper, additional experimental data are presented sustaining, on one...

Université de Neuchâtel

The quasineutrality condition in amorphous semiconductors: Reformulation of the ‘lifetime/relaxation’ criterion

Shah, Arvind ; Hubin, J. ; Platz, R. ; Goerlitzer, M. ; Wyrsch, Nicolas

In: Journal of Non-Crystalline Solids, 1996, vol. 198-200, p. 548-551

The concepts of lifetime and relaxation semiconductors introduced by van Roosbroeck and Casey are reconsidered for amorphous semiconductors and the effect of localized states on the lifetime/relaxation criterion specified: The quantity to be considered is τρ/Td, where Td is (as before) the dielectric relaxation time, but τρ is...

Université de Neuchâtel

On the transport properties of microcrystalline silicon

Fejfar, A. ; Beck, N. ; Stuchlíková, H. ; Wyrsch, Nicolas ; Torres, Pedro ; Meier, Johannes ; Shah, Arvind ; Kočka, J.

In: Journal of Non-Crystalline Solids, 1998, vol. 227-230, p. 1006-1010

To determine the charge collection mechanism in hydrogenated microcrystalline silicon (μc-Si:H) solar cells, we have measured the electronic transport properties of μc-Si:H by time-of-flight and by ac capacitance and conductance on a unique 5.6 μm thick sample. We found the electron drift mobility μD=2.8±0.2 cm2 V−1 s−1, thermally...

Université de Neuchâtel

Microcrystalline p–i–n cells: a drift-controlled device?

Wyrsch, Nicolas ; Torres, Pedro ; Meier, Johannes ; Shah, Arvind

In: Journal of Non-Crystalline Solids, 1998, vol. 227-230, p. 1272-1276

The objective of this paper is to get more insight into the physics of microcrystalline silicon based solar cell by studying electric field profiles, spectral responses and current–voltage characteristics. Based on a comparison with a-Si:H p–i–n and c-Si p–n diodes, we concluded that μc-Si:H p–i–n devices are not field-controlled despite the presence of a high electric field...