Techniques for minimizing loss of volatile components during thermal processing of kesterite films are provided. In one aspect, a method for annealing a kesterite film is provided. The method includes: placing a cover over the kesterite film; and annealing the cover and the kesterite film such that, for an entire duration of the annealing, the cover is at a temperature T1 and the kesterite film is at a temperature T2, wherein the temperature T1 is greater than or equal to the temperature T2. Optionally, during a cool down segment of the annealing, conditions can be reversed to have the temperature T1 be less than the temperature T2. A solar cell and method for formation thereof using the present annealing techniques are also provided.
