Sprayed CuInS2 thin films for solar cells: The effect of solution composition and post-deposition treatments

CuInS2 thin films were prepared by spray pyrolysis from solutions with different compositions. Etching in KCN solution and thermal treatments in vacuum and hydrogen were applied to as-deposited films. KCN etching removes conductive copper sulfide from the surface of Cu-rich films but has no effect on matrix composition. Vacuum annealing at 500°C and hydrogen treatment at 400–500°C purifies the films, prepared from the solutions with the Cu/In=1, from secondary phases, reduces chlorine content and improves crystallinity. Vacuum annealing results in n-type films due to the formation of In2O3 phase. Treatment in hydrogen reduces oxygen-containing residues and results in p-type CuInS2 films with resistivity close to 10 Ω cm.