NOVELTY - Method (M1) for forming a semiconductor material on a substrate (1210), comprises: forming a first layer (L1) above a surface of the substrate, where the first layer (L1) comprises copper, indium and gallium; forming a second layer above the first layer (L1), where the second layer comprises silver; and heating the first layer (L1) and the second layer in the presence of a chalcogen at a temperature of 100-700 degrees C.    USE - The method is useful for forming a semiconductor material on a substrate (claimed), which is useful in thin film photovoltaic devices such as solar cells.    ADVANTAGE - The method: provides the semiconductor material, which exhibits improved film morphology, higher conductivity, good thermo-mechanical stability and chemical resistance, hence provides the solar cells having improved efficiency; and is reliable, simple and cost effective, as compared to conventional methods.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) a method (M2) for forming a semiconductor material on a substrate, comprising: forming a first layer (L2) above a surface of the substrate, where the first layer (L2) comprises copper, indium, gallium and aluminum; and heating the first layer (L2) and the second layer in the presence of a chalcogen at a temperature of 100-700 degrees C; and    (2) a method (M3) for forming a semiconductor material on a substrate, comprising: forming a first layer (L3) above a surface of the substrate, where the first layer (L3) comprises copper, indium, gallium and X (where X is at least one of sodium, magnesium, potassium or calcium), and the concentration of X varies from a first interface of the first layer (L3) to a second interface of the first layer (L3); and heating the first layer (L3) and the second layer in the presence of a chalcogen at a temperature of 100-700 degrees C.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of a thin film photovoltaic device.    Thin film photovoltaic device (1200)    Absorber layer (1202)    Back contact layer (1204)    Substrate (1210)    Light-receiving surface of absorber layer (1222)