NOVELTY - A benzoimidazole compound (I), is new.    USE - New benzoimidazole compound is used for composition for organic-semiconductor material for forming coating film e.g. photoelectric-conversion layer for organic photoelectric-conversion element e.g. organic thin-film solar cell (all claimed). Uses include but are not limited to field effect transistor, photodetector, photovoltaic detector, image pick-up element, light emitting diode, laser element, amplifier, radiator for telecommunications, memory element and electrochromic element.    ADVANTAGE - The benzoimidazole compound has small band gap at near infrared region wavelength of 865 nm or more. The element containing the layer formed using the composition containing the benzoimidazole compound has excellent production aptitude and small variance of electric current value.    DETAILED DESCRIPTION - A benzoimidazole compound of formula (I), is new.    Ar'=arylene or hetero-arylene;    X=sulfur atom, oxygen atom, selenium atom, tellurium atom, -N(R1)-, or -C(R2)(R3)-;    R1=H, alkyl, alkenyl, alkynyl, aryl, or heteroaryl;    R2,R3=alkyl, alkenyl, alkynyl, aryl, or heteroaryl;    or R2+R3=ring;    Y'=electron-withdrawing group which has Hammett substituent constant of more than 0.5;and    n=2-2000.    INDEPENDENT CLAIMS are included for the following:    (1) organic photoelectric-conversion element, which comprises an electrode (11), an electrode (12), and a photoelectric-conversion layer including benzoimidazole compound (I) arranged in-between electrodes;    (2) composition, which contains compound (I) and organic solvent;    (3) benzoimidazole compound of formula (I'); and    (4) imidazole compound of formula (I").    Z1-Z5=halo or perfluoroalkane sulfonyloxy;and    Z6-Z8=halo.    When Z3 and Z4 are fluoro, Z5 is chloro, bromo, iodo or perfluoro alkane sulfonyloxy; When Z3 and Z4 are chloro or perfluoroalkane sulfonyloxy, Z5 is bromo or iodo; When Z8 is fluoro, Z6 and Z7 are chloro, bromo, or iodo; When Z8 is chloro, Z6 and Z7 are bromo or iodo; and When Z8 is bromo, Z6 and Z7 are iodo    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic side view of organic thin-film solar cell.    Transparent support (7)    Photoelectric-conversion element (10)    Electrodes (11,12)    Hole-transport layer (21)    Electron-carrying layer (22)