A numerical investigation of the intrinsic layer effect on the improvement of GaAs n-i-p solar cell performances is presented. Solution of Poisson's equation together with continuity equations for electrons and holes allows the determination of carrier's density, electric field and recombination profiles within the i-layer. The analysis examines the effect of i-layer thickness on the electric field, recombination rate and collection efficiency. It is found that increasing the i-layer thickness increases the absorption while it reduces the electric field and increases the recombination rate. The three competing parameters have to be monitored simultaneously so as to obtain an optimal thickness. To achieve this, the variation of the total photocurrent is used as indicator. The photocurrent shows a sharp increase in the domain of very thin i-layers (< 0.5 mu m) then a saturation is reached for thicker layers (> 1 mu m), the simulation is performed for thicknesses up to 2 mu m. (c) 2005 Elsevier B.V. All rights reserved.