The problem of calculating the photo-induced current in an n(+)p junction solar cell with a microstructure grating on the top is formulated. For the case where useful absorption regions lie below the grating a closed solution of the problem is obtained, in which the carrier photo-generation rate is calculated using a full-vector electromagnetic simulation technique. Two structures: filled lamellae grating and overlayer, and filled V-groove grating and overlayer are considered, The first structure is optimized with respect to the integral photo-current and the second with respect to reflection loss. Both optimized structures are much less reflective and more efficient than an optimized flat-surface Si-SiO2 layer cell. (C) 2000 Elsevier Science B.V. All rights reserved.