NOVELTY - The method comprises depositing a film layer such as a multilayer structure onto a substrate, depositing an underlying layer onto the substrate, depositing an overlying layer on the film layer, annealing the film layer, the underlying layer and the overlying layer in a vacuum and in the presence of an atmosphere of gas to remove excess material from the film layer at an average heating rate of less than 10 degrees C per second, and cooling the annealed film layer at an average cooling rate of 0.1 degrees C per second.    USE - The method is useful for manufacturing photovoltaic devices such as solar cell.    ADVANTAGE - The method is capable of efficiently and rapidly manufacturing the photovoltaic devices with high throughput and yield, excellent quality and improved performance.    DETAILED DESCRIPTION - The method comprises depositing a film layer such as a multilayer structure onto a substrate, depositing an underlying layer onto the substrate, depositing an overlying layer on the film layer, annealing the film layer, the underlying layer and the overlying layer in a vacuum and in the presence of an atmosphere of gas to remove excess material from the film layer at an average heating rate of less than 10 degrees C per second, and cooling the annealed film layer at an average cooling rate of 0.1 degrees C per second. The film layer copper indium gallium (Cu( alpha )In1-xGax)( beta ), and selenium, tellurium or sulfur, where alpha is less than beta and x is 0-1. A total concentration of copper, indium and gallium and selenium+sulfur+tellurium of the film layer is less than 30 atm.%, 30 atm.%, and 70 atm.% respectively. The film layer: is deposited in vacuum and deposited in an atmosphere comprising gases of argon, hydrogen, nitrogen, oxygen, hydrogen sulfide or hydrogen selenide; has a thickness of 0.15-8 mu m; and is deposited onto the underlying layer. The annealing step: comprises pre-heating the deposited film layer to a first temperature of less than 400 degrees C, heating the deposited film layer to a second temperature of less than 650 degrees C for less than 60 minutes, and cooling the film layer at a third temperature of less than 560 degrees C; and is performed using an external heating source and using pulse or flash annealing process. Each film layer has a same composition.