The purpose of this work is to develop a back surface field (BSF) for industrial crystalline silicon solar cells and thin-film solar cells applications. Screen-printed and sputtered BSFs have been realised on structures which already have a n(+)p back junction due to the diffusion of the phosphorus in both faces of the wafer during solar cell emitter elaboration. Rapid thermal annealing temperatures from 700degreesC to 1000degreesC have been used. Thickness of the BSF has been measured by SIMS and confronted to the theoretical expected value and simulations. Electrical and optical measurements have been done in order to characterise the BSF. For 250 pm thick industrial solar cells, 6% relative increase in photocurrent has been reached. (C) 2002 Elsevier Science B.V. Ail rights reserved.