Electroluminescence spectra were measured on textured and non-textured silicon solar cells at room temperature. From these spectra the absorptivity for band-to-band transitions A(BB)((h) over bar omega) of these solar cells could be extracted by application of the generalized Planck＇s law for the emission of luminescence via direct or indirect transitions. Our method is an alternative to the more conventional measurements of transmission and reflection and has the advantage, that only that part of the absorptivity leading to the generation of electron-hole pairs is determined, even if significant free-carrier absorption is present.