MICROWAVE PHOTOELECTROCHEMISTRY

Photocurrent measurements only monitor light induced charge carriers, which are actually leaving the electrode. Simultaneous potential dependent photoinduced microwave conductivity (PMC) measurements provide complementary information on the integral over all minority carriers, instantaneously present in the photoelectrode regardless of whether they are finally lost or released into the external circuit. Experiments with single crystal silicon electrodes show that the PMC-curves are characteristically different and complementary for p- and n- type electrodes and significantly affected by interfacial charge transfer and surface recombination. The potential dependent PMC signals were calculated and the information content of the obtained analytical expressions analysed. Among the interfacial parameters which can be evaluated and determined with microwave photoelectrochemical measurements are the flatband potential, the surface concentration of minority carriers, the rate of surface recombination and the interfacial charge transfer rate. When the absorption coefficient is known, the doping concentration and diffusion length of the electrode material are also accessible. The PMC information can also be obtained space resolved, when a laser scanning technique is used.