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A 2D Monte-Carlo model was built to calculate the probability of paths creation between the two interfaces of a TC material via direct contact between filler particles. This model allowed studying the impact of the filler size with respect to the distance between the two interfaces on the probability of direct TC paths creation. Calculation is carried-out considering one single filler size and a mixture of two fillers of different dimensions. The material was divided in a grid and the filler loading was expressed as the % of cell occupation by a particle. We demonstrated that for any degree of filler loading, it is beneficial to use large size particles compared to the distance between the two interfaces. The calculated equivalent thermal conductivity shows a maximum impact of filler particles size for 50% of cell occupation.

The photovoltaics industry is growing at a remarkable rate, more than 35% per year for the past 8 years. This reflects both the recent enlightened favourable rebates and tariff policies in several European countries and Japan but also the growing awareness of energy security and greenhouse abatement imperatives. This rapid growth is mirrored by an intense research effort which critically depends on materials research, with several complex ternary, quarternary inorganic materials being used and a raft of new organic and molecular materials as well as a growing importance of quantum confined nanostructures, which allow extra degrees of freedom in tailoring materials properties.

We study Si deposition in a low pressure chemical vapour deposition (LPCVD) system as a possible technique for the industrial production of thin-film Si solar cells. More specifically, a cost goal below 40$/m/sup 2/ for the Si-deposition was aimed at. The system consists of a lamp-heated quartz tube connected to a pump system at one end and closed with a quartz door at the other (the thermal insulation between door and reaction volume is realised by a vacuum-pumped quartz bell jar). Si layers can be grown on 20 wafers simultaneously, using a system which allows removal of the unwanted Si-deposition on the reactor walls by using a quartz insert which can be easily removed from the system. Two deposition processes have been investigated, with dichlorosilane in the range of 900-1050/spl deg/C and with silane between 750 and 900/spl deg/C. A growth rate of 0.2-0.3 /spl mu/m/min has been achieved with a small H/sub 2/-consumption/wafer. High quality epitaxial layers have been obtained, a fact illustrated by solar cells produced in layers grown on p/sup +/ monocrystalline Si substrates. Homogeneous layers have also been deposited on ceramic substrates. In spite of the small grain size, the first solar cells processed in these layers show low leakage currents.