TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Unit: The monomeric unit contains thiophene ring, fluorene ring, phenylene vinylene group and/or phenylene ethylene group. The organic thin-film solar cell has electrode layer and photoelectric-converting-layer containing photoelectric conversion material sequentially formed on substrate. The photoelectric-converting-layer is coating film.    TECHNOLOGY FOCUS - POLYMERS - Preferred Copolymer: The photoelectric-conversion material contains fluoro-thiophene copolymer. EXAMPLE - Thin silica film was formed on surface of polyethylene naphthalate film substrate having thickness of 125 microns, and patterning was carried out by etching. The pattern form on substrate was washed using acetone. The coating liquid containing water dispersible poly(3,4)-ethylene dioxythiophene was applied on patterned substrate to form hole-extraction layer having thickness of 100 nm. The hole extraction layer was then dried for 30 minutes at 150degreesC. Chloroform solution (0.3 weight%) of fluorene thiophene copolymer (poly((9,9-dihexylfluorenyl-2,7-diyl)-co-(bithiophene))) and chloroform solution of fullerene (PCBM;1-(3-methoxycarbonyl) propyl-1-phenyl (6,6)-C60) were mixed in weight ratio of 1:1 to prepare a coating liquid. The prepared coating liquid was applied on hole extraction layer, dried for 10 minutes at 110degreesC to form photoelectric-converting-layer having film thickness of 100 nm. Stokes shift of fluorene thiophene copolymer (poly((9,9-dihexylfluorenyl-2,7-diyl)-co-(bithiophene))) was 1.05 eV. The photoelectric-conversion material had favorable stokes shift and charge separation and hence had improved electric-power-generation efficiency. The organic thin-film solar film was produced using obtained photoelectric-converting-layer. The organic thin-film solar cell had excellent optical absorption characteristics, charge-separation characteristics, charge-transport characteristics, oxidation-resistant characteristics and water-resistant characteristics.