NOVELTY - The photovoltaic device comprises a flexible substrate (622), a molybdenum back-contact layer (624), a Ib-IIIb-VIb solar absorber layer, a heterojunction partner layer, a buffer layer, a transparent top contact layer, and a metallic top contact. The solar absorber layer: comprises gallium and indium, copper, selenium, silver, and tellurium; has a composition graded such that portions of the absorber layer near the back-contact layer are enriched in tellurium and depleted in selenium relative to portions of the absorber layer near the heterojunction partner layer.    USE - Used as a thin film photovoltaic device such as a solar cell.    ADVANTAGE - The photovoltaic device can be economically manufactured with high conversion efficiency, compact size, increased yield and enhanced electrical output.    DETAILED DESCRIPTION - The photovoltaic device comprises a flexible substrate (622), a molybdenum back-contact layer (624), a Ib-IIIb-VIb solar absorber layer, a heterojunction partner layer, a buffer layer, a transparent top contact layer, and a metallic top contact. The solar absorber layer: comprises gallium and indium, copper, selenium, silver, and tellurium; has a composition graded such that portions of the absorber layer near the back-contact layer are enriched in tellurium and depleted in selenium relative to portions of the absorber layer near the heterojunction partner layer, such that the portions of the absorber layer near the back-contact layer are enriched in copper and depleted in silver relative to the portions of the absorber layer near the heterojunction partner layer and such that the portions of the absorber layer near the back-contact layer are enriched in aluminum and depleted in indium relative to the portions of the absorber layer near the heterojunction partner layer; and further has the composition graded in ratio of gallium to indium such that portions of the absorber layer near the back-contact layer have a different ratio of gallium to indium relative to portions of the absorber layer near the heterojunction partner layer, the composition graded in aluminum concentration such that portions of the absorber layer near the back-contact layer have higher aluminum content relative to portions of the absorber layer near the heterojunction partner layer, the composition graded in ratio of copper to silver such that the portions of the absorber layer near the back-contact layer have a higher ratio of copper to silver than the portions of the absorber layer near the heterojunction partner layer and the composition graded in ratio of tellurium to selenium such that the portions of the absorber layer near the back-contact layer have a higher ratio of tellurium to selenium than the portions of the absorber layer near the heterojunction partner layer.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a photovoltaic device.    Substrate (622)    Molybdenum back-contact layer (624)    First sublayer (630)    Transparent conductor layer (640)    Protective layer. (644)