A photonic light trap, i.e. a combination of an angularly selective filter and a light scattering process in a solar cell, results in potentially very efficient light trapping. Angularly selective filters are investigated theoretically and experimentally. One of the filters is used to realize a photonic light trap for a thin-film solar cell with amorphous-silicon absorber layer on a roughened superstrate. We experimentally demonstrate that the light absorption in this solar cell is enhanced by 25% in a wavelength range of 700-750 nm. Accordingly, the quantum efficiency of the solar cell demonstrates an increase of 25% in the same wavelength range. (C) 2009 Elsevier B.V. All rights reserved.