Low pressure chemical vapour deposition (LP-CVD) ZnO as front transparent conductive oxide (TCO), developed at IMT, has excellent light-trapping properties for a-Si:H p-i-n single-junction and 'micromorph' (amorphousymicrocrystalline silicon) tandem solar cells. A stabilized record efficiency of 9.47% has independently been confirmed by NREL for an amorphous silicon singlejunction p-i-n cell (;1 cm ) deposited on LP-CVD ZnO coated glass. Micromorph tandem cells with an initial efficiency of

During the last two decades, the Institute of Microtechnology (IMT) has contributed in two important fields to future thin-film silicon solar cell processing and design:(1) In 1987, IMT introduced the so-called ''very high frequency glow discharge (VHF-GD)'' technique, a method that leads to a considerable enhancement in the deposition rate of amorphous and microcrystalline silicon layers. As a direct consequence of reduced plasma impedances at higher plasma excitation frequencies, silane dissociation is enhanced and the maximum energy of ions bombarding the growing surface is reduced. Due to softer ion bombardment on the growing surface, the VHF process also favours the formation of microcrystalline silicon. Based on these beneficial properties of VHF plasmas, for the growth of thin silicon films, plasma excitation frequencies f exc in the range 30-300 MHz, i.e. clearly higher than the standard 13.56 MHz, are indeed scheduled to play an important role in future production equipment.(2) In 1994, IMT pioneered a novel thin-film solar cell, the microcrystalline silicon solar cell. This new type of thinfilm absorber material--a form of crystalline silicon--opens up the way for a new concept, the so-called ''micromorph'' tandem solar cell concept. This term stands for the combination of a microcrystalline silicon bottom cell and an amorphous silicon top cell. Thanks to the lower band gap and to the stability of microcrystalline silicon solar cells, a better use of the full solar spectrum is possible, leading, thereby, to higher efficiencies than those obtained with solar cells based solely on amorphous silicon.Both the VHF-GD deposition technique and the ''micromorph'' tandem solar cell concept are considered to be essential for future thin-film PV modules, as they bear the potential for combining high-efficiency devices with low-cost manufacturing processes.

UNAXlS KAI PECVD reactors developed for AM LCD technology have been demonstrated to possess a high potential for thin film silicon solar cells based on amorphous and microcrystalline silicon. For the next generation of thin film modules with highty effective lighttrapping LP-CVD ZnO large-area deposition is developed at Unaxis as well, in combination with a very simple but effective back reflector concept. A first prototype module of 0.447 m2 active area with 7.1 % initial efficiency has been achieved for amorphous silicon. Micromorph minimodules were prepared with 9.3 % initial aperture efficiency. All important module fabrication steps are under development at Unaxis for a complete line concept. silicon TFT's on glass for flat panel displays. To react on the fast growing display market over the last ten years, different generations of large-area KAI production equipment have been developed. These KAI manufacturing systems as schematically shown in Fig. I are well approved in display production, they run 24h a day, 360 days a year at a high uptime.

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In this paper an overview of our developments towards industrialization of thin film silicon PV modules is presented. Amorphous silicon p-i-n solar cells have been developed in medium size single-chamber R&D KAI-M PECVD reactors. High initial efficiencies of 10.6 % and stabilized of 8.6 % could be achieved for a 1 cm 2 a-Si:H p-i-n solar cell of 0.20 µm thick ilayer deposited on TCO from Asahi U type (SnO 2 ). On our in-house developed LPCVD ZnO we could further improve the stabilized a-Si:H p-i-n efficiency to a similar level of 8.5 %. Incorporating such cells in commercial available front TCO of lower quality still leads to high initial mini-module aperture efficiencies (10 x 10 cm 2 ) of 9.1% and stabilized ones of 7.46% (independently measured by ESTI JRC-Ispra).Transferring the processes from the KAI-M to the industrial size 1.1x1.25 m 2 KAI-1200 R&D reactors resulted in a-Si:H modules of 110.6 W using commercial TCO, respectively 112.4 W when applying in-house developed LPCVD front ZnO. Both initial module performances have been independently measured by ESTI laboratories of JRC Ispra. A typical temperature coefficient for the module power of -0.22 %/∞C (relative loss) has been deduced from temperature dependent I-V characteristics at ESTI laboratories of JRC Ispra. Finally, micromorph mini-modules of 10 % initial aperture efficiency have been fabricated.