Operational principles of electrochemical nanoemitter solar cells for photovoltaic and photoelectrocatalytic applications

The principle design of nanoemitter solar cells is described and their multiple applicability in photoelectrochemical solar cells that operate in the regenerative photovoltaic/photoelectrocatalytic mode as well as in solid state photovoltaics, is emphasized. For sustained operation, photoelectrochemical solar energy conversion systems have to be stabilized against corrosion processes at the reactive electrolyte interface. In the nanoemitter concept, the inclusion of passive films in the cell design allows physical stabilization of photoelectrodes. The individual steps in the preparation of photovoltaic and photoelectrocatalytic electrochemical solar cells with n- and p-type Si are described and the electronic properties of nanoemitter solar cells at the solid–liquid phase boundary are analyzed. The influence of the spatially anisotropical electrostatic potential in the nanoemitter composite structures is outlined and trajectories for the excess minority carriers are deduced that explain observed spectral properties. Routes to overcome the contact potential limitation of p-Si photocathodes for light-induced H2 evolution are described and parameters that determine the photoelectrochemical current at the employed metallic nanoemitters which form highly local MOS (metal–oxide–semiconductor) structures are identified.