NOVELTY - A conjugated polymer comprises benzoxazole bithiophene-naphthyl diphenylphosphinic acid 2-phenylbenzimidazole-1-yl ester compound (I).    USE - Conjugated polymer for an electron donor material layer of an organic solar battery device, an illuminating layer of an organic electroluminescent device and an organic semiconductor layer of an organic FET (all claimed).    ADVANTAGE - The polymer is prepared by the stille reaction in a simple manner. The polymer has better film forming property and thermal stabilizing property, high current carrier moving rate, high molar light absorbing coefficient, wide application range and wide light absorbing range for improving matching degree of sunlight emitting spectrum and photoelectric converting efficiency.    DETAILED DESCRIPTION - A conjugated polymer comprises benzoxazole bithiophene-naphthyl diphenylphosphinic acid 2-phenylbenzimidazole-1-yl ester compound of formula (I).    R1,R2=1-20C alkyl;    R3=1-20C alkyl or substituted phenyl moiety of formula (Ia);    R4-R6=H, 1-20C alkyl or 1-20Calkoxy;    x=1-2;    y=0-1;    x+y=2;and    n=1-120.    INDEPENDENT CLAIMS are also included for the following:    (1) a conjugated polymer preparation method, which involves utilizing 2,7-bi-tri methyl-benzimidazolyl (2, 1-b:3, 4-b') bisthiophene compound of formula (II), 2, 7-dibromobenzimidazolyl (2,1-b:3,4-b') bisthiophene compound of formula (III) and N, N'-dibasic-2,6-dibromo-1, 4, 5, 8-naphthyl diphenylphosphinic acid 2-phenylbenzimidazole-1-yl ester compound of formula (IV) as raw materials, adding the raw materials and catalyst in organic solvent in molar ratio of m:p:q, processing stille reaction for the mixture at 60-130 degrees C in anaerobic environment for 24-72 hours to obtain conjugated polymer containing benzoxazole bithiophene-naphthyl diphenylphosphinic acid 2-phenylbenzimidazole-1-yl ester compound (I)    (2) an organic solar battery device comprising a substrate layer, an electrode layer, an optical active layer and another electrode layer, where the optical active layer comprises an electron donor material layer and an electron acceptor material layer, material of the electron donor material layer is conjugated polymer containing benzoxazole bithiophene-naphthyl diphenylphosphinic acid 2-phenylbenzimidazole-1-yl ester compound (I)    (3) an organic electroluminescent device comprising a substrate, an anode, an illuminating layer, a buffering layer and a cathode, where the material of the illuminating layer is conjugated polymer containing benzoxazole bithiophene-naphthyl diphenylphosphinic acid 2-phenylbenzimidazole-1-yl ester compound (I)    (4) an organic FET comprising a silicon substrate, an isolation layer, an organic semiconductor layer, a source electrode and a drain electrode, where the material of the organic semiconductor layer is conjugated polymer containing benzoxazole bithiophene-naphthyl diphenylphosphinic acid 2-phenylbenzimidazole-1-yl ester compound (I).    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of an organic solar battery device. '(Drawing includes non-English language text)'