Polycrystalline silicon solar cells on mullite substrates

AbstractPolycrystalline silicon layers have been grown on various alumino-silicate substrates in arapid thermal chemical vapor deposition (RTCVD) system at high temperatures (>10001C).Structural analysis shows a columnar growth with grain sizes up to 15mm and growth rates upto 5mm/min.Solar cell devices on this fine-grained Si material result in a short-circuit currentof about 13mA/cm 2 but a poor open-circuit voltage (o0.4V). Larger grains obtained by thezone melting recrystallization (ZMR) technique boosted the current up to 26.1mA/cm 2 ,thanks to the light-trapping by the mullite substrate.Best efficiency is 8.2% on a 1cm 2 cellmade on a 20mm thick poly-Si layer. r 2002 Elsevier Science B.V. All rights reserved. Keywords:Thin silicon; Ceramic; Photovolta.iic; Light-trapping 1. IntroductionAmong the alternative approaches to bulk silicon-based cells, there is the use ofpolycrystalline silicon thin films (o30mm) on low-cost substrates.Important issuesin these developments are the choice of the substrate and the growth method sincereasonably high growth rates and an overall reduction of the number of steps areessential in order to obtain a cost-effective process.As for the silicon formation,direct deposition on foreign substrates by chemical vapor deposition at elevatedtemperature (>10001C) and atmospheric pressure is suitable since it allows high