The optoelectronic properties of thin-film silicon solar cells with grating coupler as a function of the grating parameters (period size, groove height and shape) was investigated by means of an experimental study and numerical modelling. In particular, the high blue response of solar cells with rectangular shaped gratings was investigated in detail, because the measured blue response is similar to the blue response of textured solar cells although the reflection of the cell is significantly higher and comparable to cells deposited on flat substrates. To analyze the light in-coupling properties of thin-film silicon solar cells numerical simulations based on the finite integration technique (FIT) are performed. © 2006 Elsevier B.V. All rights reserved.