Photoelectrochemical Generation of Hydrogen at Electrochemically Deposited p-CdTe Films : Effect of Heat-Treatment, Surface Modification by Platinum and Surface Oxide Layer on Conversion Efficiency

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The effects of heat-treatment, Pt modification of the surface and surface oxide layer on the efficiency for the photo-electrochemical generation of hydrogen were investigated at p-CdTe films deposited electrochemically at -0.35V (vs. Ag/AgCl) from an aqueous sulfuric acid solution of pH = 1.4 containing 1M CdSO4 and 1 mM TeO2. By heat-treatment in a He atmosphere, the crystalline diameter increased and, thus, the number of grain boundaries at which effective electron-hole recombination takes place decreased. Free metallic Te existing near the surface, which acts as a recombination center, was removed by the treatment at the temperatures above 350℃. The cathodic photocurrent was increased by the heat-treatment due to these two effects. The cathodic photocurrent was decreased and even the anodic photocurrent was observed at the films treated at too high a temperature and for too long a time. The films were converted to n-type by these treatments because of the removal of the lattice Te from CdTe crystal. Pt modification, either vacuum deposition or codeposition, improved the efficiency, but the photocurrent is small, suggesting that the major reason for the low efficiency is still the bulk recombination. The oxide layer was easily formed on the CdTe films by exposure to air but dissolved by contacting with solution and had no effect on the photoelectrochemical properties of the film.
The Electrochemical Societyの論文