Three-step vapor Se/N2/vapor Se reaction of electrodeposited Cu/In/Ga precursor for preparing CuInGaSe2 thin films

•Solid Se source is used to provide Se atmosphere for selenizing Cu/In/Ga precursors.•Three-step reaction has been used to solve the common issue of Ga accumulation.•Selenization without CuGaSe2 phase formation in the first step favors the Ga diffusion.•Ga re-diffusion and significant grain growth happened during the second step.

The three-step H2Se/Ar/H2Se reaction of CuInGa precursors for preparing high-quality CuInGaSe2 thin films is extensively used to control their composition and adhesion. In this work, a non-toxic, low-cost, solid Se source is used instead of toxic H2Se gas to selenize electrodeposited Cu/In/Ga precursors by the three-step vapor Se/N2/vapor Se reaction. Experimental results reveal that the Se content of the film in the first selenization step importantly affects the Ga distribution. Incomplete selenization (0.74