Characterization of CuInSe2 single crystals for solar cell modeling studies

The behavior of the (CdZn)S/CuInSe₂ solar cell is numerically analyzed, and the attainable performances for this device type are predicted by imposing the known material parameters. Single crystals of p-type CuInSe₂ were characterized and used to fabricate heterojunction solar cells of the form n-(Cd,Zn)S/p-CuInSe₂. The experimental and computed performance data are compared. Photoluminescence measurements were performed to determine the dominant electrically active defect states in p-type crystals that simultaneously have high carrier concentrations (>or=5*10¹⁶ cm^-3) and high-carrier mobilities (>or=50 cm²/V-s). It was found that this material is dominated by two strong emission lines at 0.940 and 0.920 eV which are attributed to the defect pairs In_Cu-V_Cu and Se_Cu-Cu_In, respectively. The corresponding composition is defined by a Cu/In ration of 0.9, a Cu content around 23 at.%, and a Se excess (>or=51 at.%). An energy band diagram of this material is also proposed.