TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The negative electrode is an aluminum electrode. In the photovoltaic conversion cell, a buffer layer is: interposed between the active layer and the positive electrode, where the buffer layer is poly(3,4-ethylenedioxythiophene) and/or poly(styrene sulfonate)sodium; or interposed between the active layer and the negative electrode, where the buffer layer is a lithium fluoride layer.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The electron acceptor is fullerene derivatives such as (6,6)-phenyl-61C-butyric acid methyl ester, carbon nanotubes, perylene derivatives, and tetracyanoquinodimethane derivatives. The weight ratio of (I)/electron acceptor is 2/1 to 1/4. SPECIFIC COMPOUNDS - Use of 25 compounds (I) is specifically claimed e.g. (1,1',1",1'''-( eta 4-1,3-cyclobutadiene-1,2,3,4-tetrayl)tetrakis-(benzene))( eta 5-cyclopentadienyl)cobalt(I) of formula (Ia), (1,1',1",1'''-( eta 4-1,3-cyclobutadiene-1,2,3,4-tetrayl)tetrakis-4-n-butyl-(benzene))( eta 5-cyclopentadienyl)cobalt(I), (1,1',1",1'''-( eta 4-1,3-cyclobutadiene-1,2,3,4-tetrayl)tetrakis-(3,5-dimethoxy-benzene))( eta 5-cyclopentadienyl)cobalt(I), (1,1'-((1,2,3,4- eta )-2,4-bis(4-methoxybenzene)-1,3-cyclobutadien-1,3-diyl)bis(phenyl))( eta 5-2,4-cyclopentadien-1-yl)-cobalt(I) and (1,1'-((1,2,3,4- eta )-2,4-bis(4-nitrobenzene)-1,3-cyclobutadien-1,3-diyl)bis(phenyl))( eta 5-2,4-cyclopentadien-1-yl)-cobalt(I).    EXAMPLE - 2-Bromo-(2,2':5',2"-terthiophene-5"-carbaldehyde) (120 mg), bis(triphenylphosphine)palladium(II) (10 mg) and copper iodide (8 mg) were introduced into a flask. Distilled benzene (50 ml), 1 8-diazabicycloundec-7-ene (0.75 ml), trimethylsilylacetylene (23 mu l) and distilled water (3 mu l) were added to the reaction medium. The mixture was stirred for 24 hours in the dark at room temperature. The solvent was then evaporated under reduced pressure to give bis(2,2':5',2"-terthiophene-5"-carbaldehyde)acetylene (36 mg). Bis(2,2':5',2"-terthiophene-5"-carbaldehyde)acetylene (36 mg) and (( eta 2-dimethyl fumarate)carbonyl, eta 5-cyclopentadienyl)cobalt(I) (14 mg) were diluted in ethanol (1 ml) and tetrahydrofuran (14 ml). The reaction mixture was heated to 150 degrees C in the microwave for 45 minutes and the solvents were then evaporated under reduced pressure to give 1,1',1'',1'''-( eta 4-cyclobutadiene-tetrakis-1,2,3,4-(2,5,2',5',2''-terthiophene-5"-carbaldehyde))-( eta 5-cyclopentadienyl)cobalt(I).