NOVELTY - The photovoltaic device having a substrate configuration, comprises transparent or opaque substrates, a metal electrode layer (220), a transparent conductor layer, an absorber layer comprising a Group II-VI semiconductor compound, a window layer (260), an interface layer (250) between the absorber layer and the window layer, and a buried junction between the absorber layer and the window layer. The absorber layer and/or the interface layer comprise a thin film and/or sintered nanoparticles. The absorber layer and interface layer comprise grain sizes.    USE - Used as photovoltaic device such as copper indium gallium selenide and cadmium telluride solar cells.    ADVANTAGE - The photovoltaic device can be industrially and economically manufactured.    DETAILED DESCRIPTION - The photovoltaic device having a substrate configuration, comprises transparent or opaque substrates, a metal electrode layer (220), a transparent conductor layer, an absorber layer comprising a Group II-VI semiconductor compound, a window layer (260), an interface layer (250) between the absorber layer and the window layer, and a buried junction between the absorber layer and the window layer. The absorber layer and/or the interface layer comprise a thin film and/or sintered nanoparticles. The absorber layer and interface layer comprise grain sizes. A portion of the interface layer located next to the absorber layer comprises large grains sizes of 2-3 mu m and 0.2-0.5 mu m, and a portion of the interface layer located next to the window layer comprises small grain sizes. The interface layer comprises a Group II-VI compound. The interface layer is created by a surface treatment of the absorber layer. The surface treatment is wet etching, dry etching, sputtering, reduction, electrochemical, heat treatments and ion milling. An INDEPENDENT CLAIM is included for a process for making a photovoltaic device.    DESCRIPTION OF DRAWING(S) - The drawing shows a side view of the photovoltaic device depicting a substrate cadmium telluride (CdTe) solar cell with an interface layer.    Substrate (210)    Metal electrode layer (220)    Back contact layer (230)    CdTe absorber layer (240)    Interface layer (250)    Window layer. (260)