High-efficiency Cu(InGa)Se2 solar cells with a zinc-based buffer layer

Zinc oxide was grown by a chemical bath deposition (CBD) method. Smooth films were obtained by a mixed solution with zinc acetate (Zn(CH3COO)2) and ammonia (NH4OH). The films were preferentially oriented towards the [002] direction. The concentrations of Zn2+ and zinc complexes in a solution were numerically calculated, and it was found that the most suitable film precursor for CBD-ZnO process was Zn(OH)2. A high efficiency of 14.3% was obtained by using CBD-ZnO as a buffer layer for Cu(InGa)(SSe)2 solar cells.Magnesium hydroxide was also grown by a CBD process with magnesium acetate (Mg(CH3COO)2) as a magnesium source. The pH level, which was adjusted by the ammonia concentration, was a critical parameter for crystal growth. The surface of a sample grown with a pH level of 10.1 showed platelet-type morphology, and the film conformally coated the surface.