TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Device: At least one dye (I) has a maximum incident photon to current efficiency at a wavelength at between 300 and 600 nm when adsorbed alone in the semiconductor layer and at least another dye (II) has a maximum incident photon to current conversion efficiency at 600-850 nm when adsorbed alone in the particulate semiconductor layer. One of (I) and (II) is a (poly)methine dye the other is a ruthenium complex dye or both are (poly)methine. The polymethine dyes are preferably derived from squaric acid. The semiconductor particle layer preferably comprises three or more adsorbed dyes, one of which (III) has a maximum incident photon to current conversion efficiency at 300-550 nm, one of which (IV) has a maximum incident photon to current conversion efficiency at 550-700 nm and one of which (V) a maximum incident photon to current conversion efficiency at 700-850 nm. (V) is a bis type polymethine dye having two conjugated methine chains.    TECHNOLOGY FOCUS - ELECTRONICS - Preferred Device: The device has a maximum incident photon to current conversion efficiency of 40% in a wavelength region of 300-850 nm. The semiconductor particle layer comprises titanium dioxide particles and the charge transport layer comprises a molten salt electrolyte. EXAMPLE - In a 200 ml stainless steel-made vessel having its inner wall coated with Teflon were charged 15 g of titanium dioxide (Degussa P-25 RTM), 45 g of water, 1 g of a dispersant (Triton X-1 00 RTM), and 30 g of zirconia beads having a diameter of 0.5 mm and dispersed in a sand grinder mill at 1500 rpm for 2 hours. The zirconia beads were filtered off the dispersion. The average particle size of the dispersed titanium dioxide particles was 2.5 pm. Electrically conductive glass having an F-doped tin oxide coat (TCO Glass-LI (RTM); surface resistivity: about 30 Ohm (square)) was cut to squares with 20 mm-sides. The titanium dioxide dispersion was applied with a glass bar to the conductive side of 8 glass pieces at a time in the following manner: An adhesive tape was stuck to one end (over a 3 mm width from the edge) of the conductive surface of each glass piece, and 8 glass pieces were aligned in two lines without gap to make a 4 cm wide and 8 cm long strip with their adhesive tape-stuck edges making both sides (8 cm long) of the strip as spacers. The coating weight of the titanium dioxide particles was adjusted to 20 g/m2. After coating, the adhesive tape was removed. The coating layer was air-dried at room temperature for 1 day and then fired in an electric muffle furnace at 450 degreesC for 30 minutes. After being cooled out of the furnace, the coated glass substrate was immersed in a solution of 3x10-4 Mol/l of dye (I) (having a maximum IPCE at 300 nm or longer and shorter than 600 nm when adsorbed alone) as a first dye and 3 x10-4 Mol/l of dye (II) (having a maximum IPCE at 600 to 850 nm when adsorbed alone) as a second dye in a mixed solvent of dimethyl sulfoxide (DMSO) and ethanol (2.5/97.5 by volume; added with 40 mmol of cholic acid) for 15 hours. The dyed glass substrate was then immersed in 4-t-butylpyridine for 15 minutes, washed with ethanol, and dried spontaneously. The photosensitive layer (dye-sensitized TiO2 layer) thus formed had a thickness of 10 gm. An electrolytic solution was prepared by dissolving 0.05 mol/l of iodine and 0.65 mol/l of iodine salt of 1-methyl -3-hexyl imidazolium in methoxypropionitrile. The TiO2 electrode substrate (2 cm x 2 cm) and a Pt-deposited glass substrate of the same size were brought into contact with the electrode layer and the Pt deposit layer facing each other. The electrolytic solution was introduced into the gap between the glass substrates by making use of capillarity so as to penetrate into the TiO2 electrode. The edges of the cell were sealed with an epoxy sealing compound. There was thus obtained a photo-electrochemical cell.