NOVELTY - A composite material is formed by mixing polythiophene derivative (I) and inorganic material in mol ratio of 10-0.1:1. The inorganic material is zinc oxide, titanium oxide, cadmium sulfide, cadmium oxide, ferric oxide, tin oxide, manganese oxide, zirconium oxide, ferrous oxide, ferrosoferric oxide, silver, copper, gold, magnesium ferrite, nickel ferrite, cobalt ferrite, zinc ferrite, copper ferrite, manganese ferrite, barium ferrite, or strontium ferrite in nano size. The composite material has particle diameter of 5-30 nm.    USE - Composite material is used for electro-optical devices and solar batteries.    ADVANTAGE - The composite material overcomes the shortage of high starting oxidation level in oxidation region, low starting reduction level in reduction region and small current density of n and p-type semiconductors. The composite material has improved light absorbing and emitting property, and conductivity in whole region of scan voltage. The composite material exhibits excellent performance of p-n junction.    DETAILED DESCRIPTION - A composite material is formed by mixing polythiophene derivative of formula (I) and inorganic material in mol ratio of 10-0.1:1. The inorganic material is zinc oxide, titanium oxide, cadmium sulfide, cadmium oxide, ferric oxide, tin oxide, manganese oxide, zirconium oxide, ferrous oxide, ferrosoferric oxide, silver, copper, gold, magnesium ferrite, nickel ferrite, iron oxide (FeFe2O4) (sic), cobalt ferrite, zinc ferrite, copper ferrite, manganese ferrite, barium ferrite, or strontium ferrite in nano size. The composite material has particle diameter of 5-30 nm.    R1,R2=linear or branched 1-24C alkyl, 1-12C alkoxy, 3-8C cycloalkyl, aryl, amido, carboxyl, ester, halo, or nitro;and    n=2-10000.    An INDEPENDENT CLAIM is included for preparation of composite material. Polythiophene derivative is dissolved in an organic solvent, to prepare a saturated solution and then an inorganic material is added to the saturated solution. The obtained liquid mixture is kept in a sealed container and subjected to ultrasonic dispersion for 0.5-6 hours. Then, the solvent is removed and the resultant is dried to obtain composite material. The organic solvent is chloroform, tetrahydrofuran, dichloromethane, benzene, toluene, glycol, or isopropyl alcohol. The composite material has particle diameter preferably of 5-20 nm.