Abstract
Abstract The mechanism of formation of CuInSe2 thin films on a glassy carbon surface during voltammetric scanning was examined in detail for the first time using a combination of Pourbaix analyses, cyclic and hydrodynamic voltammetry of the binary In + Se and Cu + Se systems, along with cyclic photovoltammetry, i.e. cyclic voltammetry combined with periodic white light illumination of the electrode/electrolyte interphase, on the ternary Cu + In + Se system. A sulfuric acid matrix containing SeO2 and uncomplexed Cu2+ and In3+ ions was used in all cases. The data on the binary systems were consistent with the facile formation of a Cu2−xSe solid phase in the Cu+Se system and a kinetically sluggish interaction between In and Se in the In+Se case. An internally consistent mechanistic scheme is proposed for the ternary system involving the concurrent formation of the Cu2−xSe phase, its subsequent reduction coupled with the 6 e− reduction of H2SeO3 to H2Se, and finally the underpotential assimilation of In into the solid phase leading to the photoactive chalcopyrite semiconductor, CuInSe2. The cathodic decomposition of the initially formed Cu2−xSe is shown to be a key to subsequent assimilation of In and formation of CuInSe2. The photocathodic response observed for this thin-film formation was diagnostic of a Cu-rich ternary composition and consequent p-type behavior for the conditions pertaining to this study.
Published Version
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