Electrodeposition of CuGaSe2 from Thiocyanate-Containing Electrolytes

We report electrodeposition of CuGaSe2 from electrolytes that contain thiocyanate (SCN-) as a complexing agent to cathodically shift the reduction potential of Cu(II). In the presence of thiocyanate, the peak reduction currents for Cu(II) and Ga(III) during cyclic voltammetry occur at potentials that differ by only 80 mV, even though the standard reduction potentials of the uncomplexed species differ by about 870 mV. Stoichiometric CuGaSe2 deposits are obtained by the induced codeposition mechanism at -300 mV vs SCE and pH 2.75 from electrolytes with Cu: Ga ratios ranging from 0.5 to 1.5. The stoichiometry is controlled by the thermodynamic driving force associated with stable compound formation, as illustrated by the anodically shifted reduction peak obtained in cyclic voltammograms of electrolytes containing all three elemental species. Oxygen incorporation into the electrodeposit is observed, because electrodeposition of stoichiometric CuGaSe2 appears to be immediately followed by Ga oxidation. Methods for removing oxygen from the electrodeposited film are discussed. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3519997] All rights reserved.