NOVELTY - Electricity is generated simultaneously or separately from water decomposition. In the case where only electricity is produced, the silicide is illuminated but there is no contact with water. Otherwise contact is made with water, under illumination. Metallic and non-metallic silicides are used. The silicides have the molecular formula RSi. R is an organic, organometallic, and/or inorganic radical (or a mixture). Si represents silicon. In listed formulae, R is present as one or more atoms of Ti, Ni, Fe, Th, B (silicon tetraboride), Co, Pt, Mn, CSi/poly-CSi, Ir, N, Zi, Ta, V and Cr.    USE - Metallic or non-metallic silicides are employed for photo-electrochemical decomposition of water and/or photovoltaic electricity generation. They are used in heat generation, fuel cell technology, space- and terrestrial travel, static equipment and constructions. The principles are exploited in health care. Fossil fuel technologies are replaced, supplemented or enhanced by their use (all claimed).    ADVANTAGE - New applications are found for silicides in photovoltaic systems. Process efficiency is enhanced by heating, either self-heating or externally-supplied. Unlike the case in prior art, water impurity has little effect on its decomposition. The surface area of the silicides requires no special enhancement. Silicide reactivity in decomposing water or electricity generation is predominantly catalytic in nature. Operation is feasible above or below room temperatures and under low illumination levels. Dyes increase activity through light absorption (dye-sensitization of semiconductors). Perylene-based dyes resist high temperatures. 13 practical examples are included.    DETAILED DESCRIPTION - The silicide contains at least one silicon atom with increased electron density. The silicide acts as a catalyst and receiver of artificial and solar light. The light participates in a photo-electrical process e.g. water decomposition, and/or a photovoltaic process generating electricity. The silicides serve as electrodes in a conductive-electrolyte system. They are connected with one or more opposite electrodes. Current is generated, with or without water decomposition. The opposite electrode is conductive. It is a: metal, transition metal, metal oxide, transition metal oxide, non-metallic structure and/or mixed structure. The two types of operation, photoelectric and photovoltaic, proceed separately or in combination. The silicide is in crystalline form and the artificial light and/or sunlight is concentrated and/or diffuse. With silicide electrodes connected to conductive opposite electrodes, each with suitable doping, electrolyte can be dispensed with and the electrodes are in direct connection. The light sources and/or additional thermal energy sources emit energy in the waveband 200-15000 nm. Silicide light absorption is increased by one or more dyes. These are coupled, complexed, coated or bonded to the silicide. The dyes are perylenes and their analogs. High temperatures and light concentrations enhance reaction. Energy introduced for this purpose comes from e.g. electrical-, microwave- and/or geothermal heating. Other oxide semiconductors are listed as agents actively assisting the process. The silicides are immobilized in e.g. listed polymers or glasses. These are conductive. Numerous possible electrode dopants are listed.