In this work, we investigate the potential use of silicon nanocrystals (Si-nc) into photovoltaics technology as one possible way to increase the silicon solar efficiency at low cost. The Si-nc were prepared ex situ (pulverizing of electrochemical etched porous silicon), embedded into spin-on-glass antireflecting SiO2 based solution and then spun onto standard silicon solar cells. The Si-nc/SiO2 layer serves as a luminescence down-converter. Indeed, the high energetic photons are absorbed within the converter 'Si-nc' and transformed via its photoluminescence (PL) to red ones ( similar to 700 nm) which are then converted much more efficiently in silicon solar cell. We first quantify the size of the Si-nc. Then we present investigations of Si-nc based converter with different PL intensities and its influence on solar cell performances (internal quantum efficiency (IQE), current-voltage characteristic). We observe increase in IQE in the region where the PL of Si-nc appears. We also report the correlation between the converter PL intensity and IQE. To get insight into the potential of such converter, we introduced a simplified one-dimensional model. The results of the modelling are shown and compared with experimental data. (C) 2003 Elsevier B.V. All rights reserved.