Luminescent tellurium-doped cadmium sulphide electrodes as probes of semiconductor excited-state deactivation processes in photoelectrochemical cells

Abstract

Correlations among quantum efficiencies for photocurrent (φ_x), emission (φ_r), and non-radiative recombination (φ_nr) are discussed with reference to data from single-crystal, n-type, 100 and 1000 p.p.m. CdS: Te-based photoelectrochemical cells (PECs) employing aqueous sulphide electrolyte. These materials emit while they serve as PEC electrodes. The assumption that the proportionality of φ_r to φ_nr is unaffected by potential, leads to a simple expression relating φ_x to φ_r for monochromatic excitation. Calculated and observed emission data are in reasonable agreement; sources of deviation are discussed. Polychromatic excitation is shown to yield photocurrents and emission intensities which are approximately a weighted average of the values obtained with the constituent monochromatic frequencies. Practical implications of the φ_x correlation with φ_r are described, as are related results from other PECs.