Voltammetric study of selenium and two-stage electrodeposition of photoelectrochemically active zinc selenide semiconductor films in Ionic liquid zinc chloride-1-ethyl-3-methylimidazolium chloride

Ionic liquid zinc chloride-1-ethyl-3-methylimidazolium chloride (IL ZnCl₂-EMICl) with a ZnCl₂/EMICl ratio of 40/60 mol% was used as the electrolyte to study the voltammetric behavior of Se(IV) introduced into the IL as selenium chloride (SeCl₄) or selenium oxide (SeO₂). The electrodeposition of ZnSe was performed using constant-potential electrolysis at tungsten electrodes via a two-stage approach from the IL with and without SeO₂. The nucleation mechanism of Se at the tungsten electrodes agrees better with the three-dimensional instantaneous nucleation than the progressive nucleation based on Sharifker's model. Crystalline Se and approximately stoichiometric crystalline ZnSe electrodeposits could be obtained from this system. The ZnSe films showed photoelectrochemical activity with a bandgap energy of ∼2.5 eV. According to the experiments of the dependence of the photocurrent on the applied potential, the ZnSe film was determined to be a p-type semiconductor with the flatband potential V_FB of.0.024 V (vs. Fc/Fc⁺).