Off-stoichiometry effect on the CuInSe2 dielectric function

The dielectric function of CuInSe2 has been studied for various composition ratios of Cu/In. The crystals were cut from ingots of 10mm. diameter and 4 0mm. length, grown by the classical Bridgman method. Spectroscopic ellipsom etry measurements have been performed at room temperature in the range of 1 .5-5.5eV. From the measured spectra of the imaginary part of the dielectric function epsilon (2), the broadening effect of the Cu/In ratio has been ex amined in connection with photoluminescence measurements. All transition ed ges were found to broaden as the In content increases. The effect of copper d levels has been observed to dominate in the 2.5-3.5 eV range. (C) 2001 E lsevier Science BN. All rights reserved.