TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Cells: The photovoltaic solid stage cells have a glass substrate, an electrode layer, a layer of the porous structure and a counter electrode layer.The photovoltaic solid stage cells may also have a nonporous TiO2 layer on the electrode layer on the glass substrate.The resin layer preferably contains dye(s) that absorbs light and acts as electrical conductor.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Materials: The porous structure is a titanium dioxide (TiO2) layer.The porous structure has internal roughness of 10-1000 (ratio of internal surface area in pores and macroscopic volume of the porous layer).The porous structure may be dyed with a dye.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Materials: The monomer is a thiophene compound, especially ethylenedioxythiophene; and the oxidant is iron(III) p-toluenesulfonate.The solvent is acetonitrile and the oxidant is dissolved in n-butanol before addition.Preferred Dye: The dye is cis-X2bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II)X = chloride, bromide iodide, cyanide or thiocyanate.    TECHNOLOGY FOCUS - POLYMERS - Preferred Polymer: The resin is a polythiophene. Preferred Process: The monomer solution is applied to the surface of the structure at 0-50 degrees, preferably room temperature. After penetration, the structure is dried at room temperature, although temperatures of up to about 200 degreesC may be used to accelerate drying, so that the solvent evaporates and the polymer forms. SPECIFIC COMPOUNDS - A specific example of the porous structure is a titanium dioxide. A specific example of the monomer is ethylenedioxythiophene. A specific example of the oxidant is iron(III) p-toluenesulfonate.    EXAMPLE - A nanoporous TiO2 film was sintered (30 minutes at 450 degreesC) on glass coated with F:SnO2. The resultant semiconductor film was impregnated with a fresh solution of 0.5 g 3,4-ethylenedioxythiophene, 2.5 g iron(III) toluenesulfonate in 10 g acetonitrile and 10 g n-butanol. Evaporation of the solvent left a conducting resin coating in the nanoporous TiO2, which had a resistivity of 10 OMEGA/cm2 and was about 5 microns thick, in contact with F:SnO2-coated glass. About half the free volume of the nanoporous TiO2 film was filled with polythiophene and the porous film was completely penetrated from one side to the other.