Photoelectrochemical Characterization of Nanocrystalline ZnS :Mn^(2+) Layers

Abstract

Measurements of the photoelectrochemical properties of nanocrystalline ZnS electrodes doped with Mn^(2+) are presented and discussed. The observation of both anodic and cathodic photocurrent is direct evidence for the nanocrystalline nature of the system. In-situ photoluminescence measurements showed stable Mn^(2+) related photoluminescence over a large potential range. Due to the unfavourable kinetics of electron and hole transfer across the interface between the nanocrystallites and solution, it is concluded that recombination accounts for most of the charge carriers generated by illumination. Breakdown of the ZnS into elementary Zn and S^(2-) in solution was also observed at negative potential. This breakdown introduces new non-radiative decay paths and is responsible for the slow luminescence decrease as a function of operating time.