Editors’ Choice—Perspective—Bipolar Photoactivity: The Anomalous Case of Electrodeposited Copper Oxide Films

This Perspective addresses the use of photocurrent polarity (i.e., whether anodic or cathodic) in a photoelectrochemical (PEC) situation to assess whether a given semiconductor electrode sample behaves as an n - or p -type semiconductor. Using electrodeposited copper(I) oxide film as a sample platform, complications arising from the presence of Cu as an unwanted impurity phase and/or PEC corrosion of the oxide film in the photocurrent polarity data are discussed. Such artefacts are shown to be a possible contributory factor in many previous studies that have (erroneously) identified n -type semiconductor behavior in electrodeposited copper oxide films.