Université de Neuchâtel

High-Ts amorphous top cells for increased top cell currents in micromorph tandem cells

Platz, R. ; Hof, Ch. ; Fischer, Diego ; Meier, Johannes ; Shah, Arvind

In: Solar Energy Materials and Solar Cells, 1998, vol. 53, no. 1-2, p. 1-13

In the present paper, the authors discuss the application of amorphous p–i–n solar cells containing i-layers which are deposited at high substrate temperatures as top cells in amorphous silicon/microcrystalline silicon tandem (“micromorph”) solar cells. Increasing the substrate temperature for the deposition of intrinsic a-Si : H results in a reduced optical gap. The optical absorption is...

Université de Neuchâtel

a-Si:H/a-Si:H stacked cell from VHF-deposition in a single chamber reactor with 9% stabilized efficiency

Platz, R. ; Fischer, Diego ; Dubail, S. ; Shah, Arvind

In: Solar Energy Materials and Solar Cells, 1997, vol. 46, no. 2, p. 157-172

In the present paper we present results on a-Si:H/a-Si:H stacked cells deposited in a single-chamber reactor by the very high frequency-glow discharge (VHF-GD) deposition technique at 70 MHz. Hydrogen dilution of the i-layer yields more stable amorphous p−i−n solar cells, similar to what is observed for RF deposition. High dilution ratios of the i-layer are found to enhance contaminations....

Université de Neuchâtel

Improved equivalent circuit and analytical model for amorphous silicon solar cells and modules

Merten, J. ; Asensi, J.M. ; Voz, C. ; Shah, Arvind ; Platz, R. ; Andreu, J.

In: IEEE Transactions on Electron Devices, 1998, vol. 45, no. 2, p. 423-429

An improved equivalent circuit for hydrogenated amorphous silicon (a-Si:H) solar cells and modules is presented. It is based on the classic combination of a diode with an exponential current-voltage characteristic, of a photocurrent source plus a new term representing additional recombination losses in the i-layer of the device. This model/equivalent circuit matches the I(V) curves of a-Si:H...

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

Stability of a-Si:H prepared by hot-wire and glow discharge using H2 dilution evaluated by pulsed laser degradation

Hof, Ch. ; Ziegler, Y. ; Platz, R. ; Wyrsch, Nicolas ; Shah, Arvind

In: Journal of Non-Crystalline Solids, 1998, vol. 227-230, p. 287-291

The quality of intrinsic amorphous silicon films prepared by different deposition techniques was investigated. For very high frequency glow discharge, both the substrate temperature as well as the hydrogen dilution were varied. These layers were compared to hot wire material produced at comparable temperatures. To study the stability of these films, an optimised degradation method was developed...

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...

Université de Neuchâtel

Towards high-efficiency thin-film silicon solar cells with the “micromorph” concept

Meier, Johannes ; Dubail, S. ; Platz, R. ; Torres, Pedro ; Kroll, U. ; Anna Selvan, J. A. ; Pellaton Vaucher, N. ; Hof, Ch. ; Fischer, D. ; Keppner, Herbert ; Flückiger, R. ; Shah, Arvind ; Shklover, V. ; Ufert, K. -D.

In: Solar Energy Materials and Solar Cells, 1997, vol. 49, no. 1-4, p. 35-44

Tandem solar cells with a microcrystalline silicon bottom cell (1 eV gap) and an amorphous-silicon top cell (1.7 eV gap) have recently been introduced by the authors; they were designated as “micromorph” tandem cells. As of now, stabilised efficiencies of 11.2% have been achieved for micromorph tandem cells, whereas a 10.7% cell is confirmed by ISE Freiburg. Micromorph cells show a rather low...

Université de Neuchâtel

More stable low gap a-Si:H layers deposited by PE-CVD at moderately high temperature with hydrogen dilution

Ziegler, Y. ; Daudrix, V. ; Droz, C. ; Platz, R. ; Wyrsch, Nicolas ; Shah, Arvind

In: Solar Energy Materials and Solar Cells, 2001, vol. 66, no. 1-4, p. 413-419

In the present work, several series with variation of deposition parameters such as hydrogen dilution ratio, VHF-power and plasma excitation frequency fexc have been extensively analyzed. Compared with “conventional” more-stable layers obtained at 200–250°C and high H2 dilution ratios of about 10, it was observed that electrical transport properties after...

Université de Neuchâtel

Intrinsic microcrystalline silicon by plasma-enhanced chemical vapor deposition from dichlorosilane

Platz, R. ; Wagner, S.

In: Applied Physics Letters, 1992, vol. 73, no. 9, p. 1236-1238

Microcrystalline silicon (µc-Si:H) of truly intrinsic character can be deposited by plasma-enhanced chemical vapor deposition (PECVD) when dichlorosilane (SiH2Cl2) is added. A dark conductivity of 1.6 × 10–8 S/cm and an activation energy of 0.62 eV are obtained. No special gas purification or microdoping is required. SiH2Cl2 in...