Polycrystalline silicon layers have been grown on various alumino-silicate substrates in a rapid thermal chemical vapor deposition (RTCVD) system at high temperatures (> 1000degreesC). Structural analysis shows a columnar growth with grain sizes up to 15 gm and growth rates up to 5 mum/min. Solar cell devices on this fine-grained Si material result in a short-circuit current of about 13 mA/cm(2) but a poor open-circuit voltage (<0.4V). Larger grains obtained by the zone melting recrystallization (ZMR) technique boosted the current up to 26.1 mA/cm(2) 2, thanks to the light-trapping by the mullite substrate. Best efficiency is 8.2% on a 1 cm 2 cell made on a 20mum thick poly-Si layer. (C) 2002 Elsevier Science B.V. All rights reserved.