NOVELTY - The method for forming a group IBIIIAVIA compound solar cell absorber layer on a base, comprises forming a precursor on the base, reacting the precursor with selenium at 400-600 degrees C in an atmosphere having gaseous selenium species, and forming the compound layer on the base. The precursor is formed by growing a first metallic layer having a thickness of 200 nm on the base, and depositing a second layer on the first layer. A molar ratio of tellurium to gallium in the precursor is 0.05-0.5. The step of growing the first layer or depositing the second layer introduces selenium into the precursor.    USE - The method is useful for forming a group IBIIIAVIA compound solar cell absorber layer on a base for forming solar cell, where the group IB is copper, the group IIIA is gallium and the group VIA is selenium and tellurium (all claimed).    ADVANTAGE - The method enables easy, economical and uniform formation of group IBIIIAVIA compound solar cell absorber layer on the base with increased optical band-gap by effectively controlling the molar ratio of materials to increase an open circuit voltage of the solar cell thus forming the solar cell with high-efficiency and high-throughput at reduced cost.    DETAILED DESCRIPTION - The method for forming a group IBIIIAVIA compound solar cell absorber layer on a base, comprises forming a precursor on the base, reacting the precursor with selenium at 400-600 degrees C in an atmosphere having gaseous selenium species, and forming the compound layer on the base. The precursor is formed by growing a first metallic layer having a thickness of 200 nm on the base, and depositing a second layer on the first layer. A molar ratio of tellurium to gallium in the precursor is 0.05-0.5. The step of growing the first layer or depositing the second layer introduces selenium into the precursor. The solar cell absorber layer has a top surface and a bottom surface, where the bottom surface is adjacent to the surface of the base, and the indium and gallium materials are distributed uniformly between the top surface and the bottom surface. The first metallic layer is electro-deposited over the base. INDEPENDENT CLAIMS are included for:    (1) a precursor structure for forming a solar cell absorber on a surface of a base; and    (2) a solar cell absorber layer.    DESCRIPTION OF DRAWING(S) - The diagram shows process steps for forming a group IBIIIAVIA compound solar cell absorber layer on a base.