Ionic Electrodeposition of II–VI and III–V Compounds: I . Development of a Simple, Butler‐Volmer Equation‐Based Kinetic Model for Electrodeposition

Abstract

A simple kinetic model has been developed for the electrodeposition of normalCdTe and other 12–16 (II–VI) or 13–15 (III–V) compounds from solutions containing reducible ions of both constituents and is based upon a generalized Butler‐Volmer equation that considers ion transport limitations near the cathode. Although the deposition itself is a non‐equilibrium process, the reaction between the plated cadmium and tellurium is assumed sufficiently rapid that any infinitesimally small volume in the deposit remains in quasi‐chemical equilibrium, as defined by the equilibrium constant‐mass action expression involving the activities of the solid constituents and conservation of mass, as invoked by a unity mole fraction sum. Exponential activity coefficients are postulated consistent with “regular” solution models. Although neglecting second‐order effects such as hydrogen generation, IR and space‐charge voltage drops within the deposit, and possible phase segregation, the model yields a convenient algorithm to numerically simulate voltammetric (j‐E) curves and calculate the mole fractions and activities of cadmium, tellurium, and cadmium telluride existing at the deposit surface for any deposition potential.

Applications of Electrochemistry in the Fabrication and Characterization of Thin‐Film Solar Cells

“…Danaher and Lyons [65] , on the other hand, assumed that the fi rst step in CdTe deposition involves the six -electron reduction of HTeO 2 + to H 2 Te, which then reacts with Cd 2 + to form CdTe, whereas Engelken and Vandoren [66] proposed that CdTe is formed as a consequence of a solid -state reaction between Cd and Te. A more detailed model involving free and occupied adsorption sites on the growing CdTe deposit was developed by Sella et al .…”

Properties and mechanism of solar absorber CdTe thin film synthesis by unipolar galvanic pulsed electrodeposition

“…Once the precursors are reduced to elemental Cd 0 and Te 0 , CdTe formation takes place by solid-state reaction over the substrate as shown below [33,34],…”

Ionic Electrodeposition Simulation of CdTe Thin Films

“…The main simplifying assumptions and approximations in this simulation are as follows: the solution is stationary with no stirring and negligible thermal convection currents, to avoid the dependence of the cathodic diffusion-limited current density on the agitation-dependent diffusion layer thickness. According to the assumption of Engelken and Van Doren, 13 the cathode reference voltage is assumed to be completely dropped across the double layer at the deposit-electrolyte interface. This implies that the electrolyte is very conductive, the voltage drops in the deposit bulk or surface spacecharge regions are compensated for or are insignificant, and that the electrochemical reactions and/or ion mass transport are the rate-determining steps.…”