Stability and Corrosion of Semiconductors in Photoelectrochemical Solar Cells

Solar energy converting semiconductor-electrolyte systems are reviewed. The challenge of achieving stabilization is emphasized, which is needed for any envisaged technological application. The part on "fundamentals" includes equilibration issues between semiconductor and redox electrolytes, a short version of the classical description of charge transfer and dark as well as photocurrents in the framework of the Marcus-Gerischer theory and an extended overview on stabilization approaches. The two main concepts that are being followed, that is, the use of "surface transformation layers" where insoluble corrosion products are optimized to form protective films and the coating with ALD films, preferably titania, are explained in more detail. In the second part of this review, entitled "application and devices," the main systems that achieved high efficiency and/or high stability in unassisted photoelectrochemical water splitting are described. They are based on photovoltaic dual junction tandem solar cells that have been surface conditioned with interfacial layers and electrocatalysts and use the buried junction split of the quasi-Fermi level for the catalysis in a floating two-electrode configuration.