Copper Indium Dichalcogenides

Copper-indium diselenide, CuInSe2 (CIS), is a widely electrodeposited compound, due to its significance in thin film photovoltaics. 

A procedure involving (a) the deposition of nearly stoichiometric films of copper and indium on suitable substrates using vacuum evaporation or electrodeposition and (b) the heat treatment of Cu-In films in a hydrogen-selenium atmosphere at temperatures above 630 °C was reported to yield large grain (several mm in size), stoichiometric thin films of chalcopyrite CIS with a preferred 112 orientation [167]. 

Ueno et al. [172] observed that CuInSe2/Ti with a composition close to the stoichiometric ratio (slight excess of metallic components) could be deposited exclusively at a specific potential value (-0.8 V vs. SCE) from a pH 1 bath of uncom-plexed precursors at 50-55 A positive shift in the potential was seen to result in the co-deposition of a Cu3Sc2 phase (umangite), while a negative shift led to contamination by metallic indium. On the basis of measured electrolysis charge, the overall reaction of the optimum cathodic process was considered to involve the transfer of 13 electrons per mole of the product  

Based on voltammetry and solid-state characterization results. Pettier and Maurin [175] defined the electrochemical conditions leading to the formation of smooth crystalline deposits of CuInSe2 and also of the related binary compounds 

Cu9ln4 and Cu2Se. They performed electrodeposition potentiostatically at room temperature on Ti or Ni rotating disk electrodes from acidic, citrate-buffered solutions. It was shown that the formation of crystalline definite compounds is correlated with a slow surface process, which induced a plateau on the polarization curves. The use of citrate ions was found to shift the copper deposition potential in the negative direction, lower the plateau current, and slow down the interfacial reactions. 

The surface and interface conditioning procedures presented here are predominantly related to the development of photovoltaic soUd-state and electrochemical 

Rgure 2.75 Comparison of nonresonant X-ray emission spectroscopy (NXES) data for standards and after chemical/electrochemical treatments the energy region of transitions from the upper valence band of the SL  

XES spectra for as-deposited CulnSj (a), a CuS reference (b), a CulnS2 crystal (c), after KCN etching of the thin film (d), and for two 

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