Thin film photovoltaic devices are provided. The device includes a transparent substrate; a transparent conductive oxide layer on the transparent substrate; an n-type window layer on the transparent conductive oxide layer, an absorber layer on the n-type window layer, and a back contact layer on the absorber layer. The n-type window layer includes a plurality of nanoparticles spatially distributed within a medium, with the nanoparticles comprising cadmium sulfide. In one embodiment, the medium has an optical bandgap that is greater than about 3.0 eV (e.g., includes a material other than cadmium sulfide). Methods are also provided for such thin film photovoltaic devices.