Small silver (Ag) nanoparticles (with diameter smaller than 50 nm) can lead to a resonant light absorption accompanied by an enhanced electromagnetic field in their vicinity when they are irradiated by light due to so-called localized surface plasmon. In order to study the influence of metal nanoparticles in thin-film silicon solar cells in more detail, a photosensitive test structure based on a-Si:H and consisting of a TCO/(nanoparticles)/i/n/TCO layer stack was realized. A higher quantum efficiency of the test structure is achieved for wavelengths longer than 800 nm compared to the structure without nanoparticles. As a-Si:H only efficiently absorbs light for wavelenghts of up to 800 nm, the enhanced photocurrent cannot be explained by improved light absorption in a-Si:H. (C) 2009 Elsevier B.V. All rights reserved.