Electroluminescence Transient and Its Application to Kinetic Study on Electrode Reactions Caused by Carrier Tunneling in Semiconductor Electrodes

Abstract

A new method for studying electrode kinetics at a semiconductor‐electrolyte interface is proposed. An n‐type semiconductor is first put at the depletion mode by a large anodic bias with which a majority carrier (electron) tunneling takes place from the electrolyte to the semiconductor, leaving reaction (oxidation) intermediates such as . When the semiconductor is put at the accumulation mode by a large cathodic bias , after some time interval during which the external bias is kept 0 V, the electron transfer from the conduction band to the intermediates produced during anodic period takes place, accompanying light emission (electroluminescence). By varying , the lifetime of the intermediates can be estimated. Practical measurements were made by using polycrystalline prepared by the sol‐gel method, which allowed a large tunnel current. It was found that oxidation intermediates disappeared from the surface by a second‐order chemical reaction with a half‐life of about 5000 s.