Sprayed CuInS2 films grown under Cu-rich conditions as absorbers for solar cells

CuInS2 films were prepared by the spray pyrolysis method using either copper-rich solutions or the recrystallization of low-crystallinity film in the presence of an intentionally deposited CuxS layer. KCN-etched films were characterized by XRD, SEM and EDX. The Cu/In molar ratio of 1.5-4.0 in the solution resulted in well-crystallized CuInS2 films with the mean crystallite size of 120 nm. SEM study showed nonuniform surface with irregularly placed large grain domains in the flat film. The two-step process resulted in a uniform film with the crystallite size of 50 nm. Films exhibited an In-rich composition. Solar cells based on a recrystallized absorber showed an improved quantum efficiency spectrum.