Anomalous Photocathodic Behavior of CdS within the Urbach Tail Region

A series of cadmium sulfide materials have been prepared using microwave-assisted hydrolysis of cadmium−thiourea complexes in water and nonaqueous solvents. Materials are characterized using X-ray diffraction, scanning electron microscopy, diffuse reflectance spectroscopy, and various photoelectrochemical techniques. Sulfur-doped samples of CdS exhibit a pronounced photoelectrochemical photocurrent switching effect within low-energy tails of their absorption spectra. A mechanism of the photocurrent switching process is presented on the basis of experimental investigations and quantum−chemical calculations.