An Analysis of Charge Transfer Rate Constants for Semiconductor/Liquid Interfaces

Although a variety of heterogeneous rate constant data is now available at metal electrodes (1, 2), relatively little kinetic information has been obtained at semiconductor electrodes (3). Several recent experiments have indicated that the rates of charge transfer at semiconductor/liquid interfaces can vary from picoseconds to milliseconds (4-7); thus, a wide range of timescales are apparently important in the dynamics of semiconductor photoelectrochemistry. The experiments that yield long decay times have often been interpreted in the same general framework as those that yield short carrier lifetimes; yet, the various types of kinetic experiments actually differ substantially in their design and kinetic interpretation. This review presents a unified treatment of the kinetics of the various charge transfer experiments and presents estimates of the timescales that can be expected for these reactions