Schottky-junction, photoelectrochemical cells

In principle, photoelectrochemical cells can be used for the conversion of solar energy into electrical energy or for the production of a storable fuel. The first type (regenerative cells) consists of a semiconductor and inert counter electrode and a redox system in the electrolyte. The current-voltage behaviour is described by the diode equation, which is also valid for pure solid state devices (pn-junction, Schottky diode) i.e. 

Photovoltaic devices are based on the concept of charge separation at an interface of two materials having different conduction mechanisms, normally between solid-state materials, either n- and p-type regions with electron and hole majority carriers in a single semiconductor material, heterojunctions between different semiconductors, or semiconductor-metal (Schottky) junctions. In photoelectrochemical cells, the junctions are semiconductor-electrolyte interfaces. In recent years, despite prolonged effort, disillusion has grown about the prospects of electrochemical photo-... 

Assuming a quantum efficiency of unity, then /e is the photocurrent of the cell. The maximum conversion efficiency is defined by Eq. (11.5). It can be calculated for semiconductors of different bandgaps from Eqs. (11.5) and (11.12). The results are presented in Fig. 11.9. The highest efficiency is 28 % at g = 1.2 eV. This calculation is valid for solid state photovoltaic devices (p-n junction, Schottky junction) as well as for a photoelectrochemical photovoltaic cell. 

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