A solar energy collector and process for its preparation are disclosed in which the collector comprises spaced apart wall members in which one wall member is adapted to face solar radiation, and the other wall member is spaced on the remote side of the first wall member and adapted to contact a heat-absorbing medium. A foil, disposed between the wall members, has coatings on its opposite sides. The side of the foil facing the wall member receiving solar radiation has a solar selective coating, and the other side of the foil facing the other wall member has an emissive coating providing relatively high emissivity in the infrared spectrum. Preferably, the foil is metallic and precoated prior to assembling with other parts of the solar collector.