Photo-electrochemical studies on intercalation and semiconducting intercalation compounds
Abstract Many materials which can form or are intercalation compounds have semiconducting properties and exhibit photo-effects in contact with suitable electrolytes. These photo-effects are produced by electronic transitions which are facilitating subsequent ion transfer across the liquid junction interface. Various aspects of these photo-induced ionic mechanisms are discussed on the basis of selected experimental results obtained with host materials of the composition MX, MX2, MPX3, M3PX4, M6PX5Hal, MO2, and (CH)n (with M = metal, X = S, Se; P = phosphorus, Hal = halogene, O = oxygen, C = carbon, and H = hydrogen). Since light-induced insertion or deintercalation of guest species changes the free energy and solid state properties of electrode systems, these phenomena could become useful for solar energy conversion ans storage as well as for optical information storage. In addition, it is shown that photo-electrochemical techniques are a versatile tool for the study of ionic processes at interfaces.