Effects of Cu-In precursor film phase structure on CuInSe₂ film properties

The effect of sputtering power on the phase structures of Cu-In precursors and the properties of CuInSe₂ (CIS) films were investigated. Cu-In precursors were prepared using a middle frequency AC magnetron at different sputtering powers. CuInSe₂ films were formed by selenization in a selenium atmosphere. SEM and EDX were used to observe the surface morphologies and to determine the atomic concentrations in both the Cu-In precursors and the CIS films. Their microstructures were characterized by XRD. The kinetics of the reactions in the film were also analyzed. The results show that the Cu-In precursors are mainly composed of a Cu₁₁In₉ phase, with or without a CuIn phase depending on the sputtering power. Stoichiometric CIS films with a single chalcopyrite phase were synthesized from Cu-In precursors containing the Cu₁₁In₉ phase and the CuIn phase. The Cu₂Se phase occurs in addition to the CIS chalcopyrite phase in Cu-rich CIS films formed using a Cu-In precursor with the Cu₁₁In₉ phase. The Cu-In precursor with Cu₁₁In₉ and CuIn phases is favorable for CuInSe₂ absorbers in solar cells.