NOVELTY - The method comprises providing a metal alloy (18) having a uniform first bulk composition and a first surface composition, annealing the metal alloy to alter the first bulk composition and the first surface composition to provide an annealed metal alloy having a non-uniform second bulk composition and a second surface composition, and contacting the annealed metal alloy with vapors of selenium and/or sulfur to produce a selenized or a sulfurized metal alloy. The metal alloy is contacted by disposing the metal alloy in an inert atmosphere.    USE - The method is useful for preparing an absorber layer for thin film photovoltaic cells such as solar cells.    ADVANTAGE - The method is capable of simply, efficiently, rapidly and economically preparing an absorber layer of the thin film photovoltaic cells with improved conversion efficiency, reduced electrical loss and less number of process steps.    DETAILED DESCRIPTION - The method comprises providing a metal alloy (18) having a uniform first bulk composition and a first surface composition, annealing the metal alloy to alter the first bulk composition and the first surface composition to provide an annealed metal alloy having a non uniform second bulk composition and a second surface composition, and contacting the annealed metal alloy with vapors of selenium and/or sulfur to produce a selenized or a sulfurized metal alloy. The metal alloy is contacted by disposing the metal alloy in an inert atmosphere, and heating selenium and/or sulfur to form vapors that contact the metal alloy. The metal alloy is annealed by heating the metal alloy at 200-600 degrees C, and diffusing lower melting metals in the metal alloy to the surface of the metal alloy resulting in an increase in an atomic percentage of the lower melting metals in the surface of the metal alloy. The method further comprises disposing a buffer layer over the surface of the selenized or the sulfurized metal alloy and/or disposing a front contact layer over the surface of the selenized or the sulfurized metal alloy, coupling the metal alloy to a substrate, diffusing a lower melting point metal in a metal alloy to a surface of the metal alloy to define a portion (10) of a solar cell, and providing a metal alloy having multiple layers of a solar cell without sequential deposition and without co-evaporation. An INDEPENDENT CLAIM is included for a system for preparing an absorber layer for thin film photovoltaic cells.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of the formation of portion of the solar cell.    Portion of the solar cell (10)    First layer (12)    Second layer (14)    Base metal alloy (18)    Surface layer (19)    Bulk layer. (21)