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

Optical, electrical and mechanical properties of the tantalum oxynitride thin films deposited by pulsing reactive gas sputtering

Le Dréo, H. ; Banakh, Oksana ; Keppner, Herbert ; Steinmann, P.-A. ; Briand, Danick ; de Rooij, Nicolaas F.

In: Thin Solid Films, 2006, vol. 515, no. 3, p. 952-956

Thin films of tantalum oxynitride were prepared by reactive magnetron sputtering using a Ta target and N2 and O2 as reactive gases. The nitrogen flow was kept constant while the oxygen flow was pulsed periodically. The film composition evolves progressively from TaO0.25N1.51 to TaO2.42N0.25 while increasing the oxygen pulse duty...

Université de Neuchâtel

Metallo-organic low-pressure chemical vapor deposition of Ta2O5 using TaC12H30O5N as precursor for batch fabrication of microsystems

Briand, Danick ; Mondin, Gianni ; Jenny, Sabine ; van der Wal, Peter D. ; Jeanneret, Sylvain ; de Rooij, Nicolaas F. ; Banakh, Oksana ; Keppner, Herbert

In: Thin Solid Films, 2005, vol. 493, no. 1-2, p. 6-12

Ta2O5 thin films were produced by metallo-organic low pressure chemical vapor deposition using Tantalum(V) Tetraethoxydimethylaminoethoxide (TaC12H30O5N) as precursor. This liquid precursor at room temperature makes it possible to deposit thin films of Ta2O5 on wafer batches of up to 35 wafers. In this communication, we...

Université de Neuchâtel

Scope of VHF plasma deposition for thin-film silicon solar cells

Keppner, Herbert ; Kroll, U. ; Torres, Pedro ; Meier, Johannes ; Fischer, Diego ; Goetz, M. ; Tscharner, R. ; Shah, Arvind

In: Conference Record of the 25th IEEE Photovoltaic Specialists Conference, 1996, p. 669-672

The world-wide attempts in obtaining thin-film crystalline silicon are reviewed. Based on literature published so far, it appears that high-temperature manufacturing steps seem to be unavoidable for obtaining high conversion efficiencies of crystalline silicon based solar cells. High process temperatures are in contradiction for the use of low-cost substrates like e.g. glass or aluminium. Such...

Université de Neuchâtel

Preparation of undoped and doped microcrystalline silicon(μc-Si:H) by VHF-GD for p-i-n solar cells

Flückiger, R. ; Meier, Johannes ; Keppner, Herbert ; Goetz, M. ; Shah, Arvind

In: Conference Record of the 23th IEEE Photovoltaic Specialists Conference, 1993, p. 839-844

The electronic transport properties of μc-Si:H materials were investigated. The μc-Si:H was deposited by the very high frequency-glow discharge (VHF-GD) technique at an RF-excitation of 70 MHz. Very thin

doped layers (100-400 Å) were studied. Conductivities higher than 10-3 (Ω cm)-1 could be achieved for films thicker than 150 Å. The as-deposited μc-Si:H is a slightly...

Université de Neuchâtel

Intrinsic microcrystalline silicon (μc-Si:H)-a promising newthin film solar cell material

Meier, Johannes ; Dubail, S. ; Flückiger, R. ; Fischer, Diego ; Keppner, Herbert ; Shah, Arvind

In: Conference Record of the Twenty Fourth IEEE Photovoltaic Specialists Conference (1994 IEEE First World Conference on Photovoltaic Energy Conversion), 1994, vol. 1, p. 409-412

“Compensated” microcrystalline silicon is obtained by adding 8-20 ppm diborane in the plasma gas phase. p-i-n cells with such i-layers have increased infrared sensitivity when compared to a-Si:H p-i-n cells. The preparation of the world's first “mixed stacked” a-Si:H/μc-Si:H tandem cell with an initial efficiency of 9.1% is reported. The μc-Si:H cells showed no degradation of the cell...

Université de Neuchâtel

Amorphous silicon p-i-n diodes, deposited by the VHF-GD process: new experimental results

Chabloz, P. ; Keppner, Herbert ; Fischer, Diego ; Link, D. ; Shah, Arvind

In: Journal of Non-Crystalline Solids, 1996, vol. 198-200, p. 1159-1162

a-Si:H i-layers were deposited at different substrate temperatures and plasma excitation frequencies, while the other deposition parameters were kept constant. These layers were characterised by measuring the intrinsic mechanical stress and the defect density. At deposition temperatures of 200 to 250°C low stress and a low defect density were obtained for excitation frequencies between 60 and 70...

Université de Neuchâtel

Structural properties and electronic transport in intrinsic microcrystalline silicon deposited by the VHF-GD technique

Goerlitzer, M. ; Torres, Pedro ; Beck, N. ; Wyrsch, Nicolas ; Keppner, Herbert ; Pohl, J. ; Shah, Arvind

In: Journal of Non-Crystalline Solids, 1998, vol. 227-230, p. 996-1000

A series of microcrystalline samples was deposited by the very high frequency glow discharge (VHF-GD) technique, with various input powers while keeping all the other parameters of deposition constant. The goal was to correlate transport and structural properties and avoid as much as possible the problem of a variation of the Fermi level between the samples. The observed decrease of the...

Université de Neuchâtel

Recent progress in micromorph solar cells

Meier, Johannes ; Dubail, S. ; Cuperus, J. ; Kroll, U. ; Platz, R. ; Torres, Pedro ; Anna Selvan, J. A. ; Pernet, P. ; Beck, N. ; Pellaton Vaucher, N. ; Hof, Ch. ; Fischer, Diego ; Keppner, Herbert ; Shah, Arvind

In: Journal of Non-Crystalline Solids, 1998, vol. 227-230, p. 1250-1256

Recently, we have demonstrated that intrinsic hydrogenated microcrystalline silicon, as deposited by the very high frequency glow-discharge technique, can be used as the active layers of p–i–n solar cells. Our microcrystalline silicon represents a new form of thin film crystalline silicon that can be deposited (in contrast to any other approach found in literature) at substrate temperatures...

Université de Neuchâtel

Thin-film silicon solar cells: A review and selected trends

Shah, Arvind ; Platz, R. ; Keppner, Herbert

In: Solar Energy Materials and Solar Cells, 1995, vol. 38, no. 1-4, p. 501-520

A case is developed for considering silicon as the prime medium-term candidate for semiconductor photovoltaic cells; the argumentation is based on other materials not being abundantly available, highly toxic and/or very expensive. Crystalline silicon solar cells have excellent efficiencies, however, according to data presented by the authors on material fluxes and energy consumption there...