NEST: New and enhanced silicon thin-film solar cells

• Research unit: EU RFP
• Project number: 96.0340

Key words (English)

Amorphous; microcristalline; silicon; solar cells

Alternative project number (English)

EU project number: JOR3-CT97-0145

Research programs (English)

EU-programme: 4. Frame Research Programme - 5.1 Nonnuclear energies

Short description (English)

See abstract

Partners and International Organizations (English)

Laboratory of Plasma Chemistry (LPC), Université de Patras, Grece, coordinateur du projet; Laboratoire de physique des interfaces et des couches mince; (LPICM), CNRS, Palaiseau, France; Institut für Schicht und lonentechnik, Kernforschungszentrum; Jülich, Jülich, Allemagne; Institut of Physics, Academy of Sciences of the Czech Republic; Prague, Rép. Tchéque

Abstract (English)

The main goal of this project is to prepare a new type of thin-film silicon solar cells with a stable efficiency of at least 10 %. This new structure is based on the so-called 'micromorph' cell (developed at IMT by our group), which consists of a tandem structure with a top amorphous silicon (a-Si:H) cell and a bottom microcristalline silicon (mc-Si:H) cell, but deposited in the 'inverted' configuration. In the regular configuration the light enters the device through the substrates (more exactly the superstrate), while in the 'inverted' structure, enters directly the top cell (through an antireflecting coating). The main advantages include mainly a wider range of deposition temperatures (the top cell becomes less sensitive to higher deposition temperatures) for better balancing of the two component cells, and a larger choice of possible substrates (including non-transparent and/or flexible ones).
In this project, the principle role of IMT is to develop the 'inverted' mc-Si:H cells, to integrate them in complete tandem devices and characterise the latter. IMT is also involved in the deposition of intrinsic mc-Si:H layer at high deposition rates (by VHF glow discharge) and their incorporation in ~c-Si:H solar cells.
During the first year of this project, IMT developed a mc-Si:H process for inverted cell fabrication with more than 6% stable efficiency and more than 5 A's deposition rate. Cells have been deposited on various substrates including Ag/ZnO-coated glass, Asahi (5n02-coated glass), ZnO-coated aluminium and ZnO-coated stainless steel. First complete 'inverted' micromorph devices have been fabricated in collaboration with the Jülich group with 9.3 % initial efficiency on AgIZnO-coated glass. Other complete devices have also been fabricated at MT on aluminium and stainless substrates with efficiencies higher than 9.2 % (initial).
Reasonable mc-Si:H single-junction cells have also been deposited at deposition rates as high as 10 A/s (10.7 A/s with 5.2 % efficiency). A combination of VHF glow discharge and hotwire lead to mc-Si:H deposition rates of 25 A/s, with resulting low-defect density layers, but so far poor device properties.

References in databases (English)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 96.0340