COMPUTER-SIMULATION OF CDTE ELECTRODEPOSITION

Following the simple kinetic model, based on the Butler-Volmer equation, developed by Engelken and Van Doren, a computer simulation has been performed of CdTe electrodeposition at 160-degrees-C from a special ethylene glycol-based bath containing CdCl2 (1 M), TeCl4 (0.01 M) and KI (0.3 M). From the fitting of the experimental data, the values of the thermodynamic, kinetic and mass transport parameters of the electrodeposition process were obtained. Other simulations in which the influence of Cd and Te concentrations in the electrolyte has been analysed proved that the given bath composition has been optimized to obtain electronic-grade CdTe over a wide range of deposition potentials (more than 50 mV around the point of perfect stoichiometry). They also showed that, as a consequence of the high ratio between the Cd and Te concentrations in solution, the potential ot perfect stoichiometry is less negative than the Cd Nernst potential, so that Cd underpotential deposition is possible. The results have been discussed within the framework of those obtained by Engelken and Van Doren in aqueous solution.