NOVELTY - A nitrogen atom-containing organic compound (I)-(IV), is new.    USE - New nitrogen atom-containing organic compound is used for composition for forming film e.g. photoelectric conversion film of organic thin-film solar cell (all claimed). Uses include but are not limited to field effect transistor, infrared photodetector, photovoltaic detector, medical image photograph system, light emitting diode, laser element, amplifier and radiator for telecommunications, holographic memory element and electrochromic display.    ADVANTAGE - The film formed using the composition containing the nitrogen atom-containing organic compound provides organic thin-film solar cell having excellent photoelectric conversion efficiency.    DETAILED DESCRIPTION - A nitrogen atom-containing organic compound of formulae (I)-(IV), is new.    R11=H, acyl, alkoxycarbonyl, alkyl, fluoro, aryl, carbamoyl, carboxy or -Rc=CRaRb;    Ra,Rb=alkyl, cyano, alkoxycarbonyl or acyl, in which one of Ra and Rb is cyano, alkoxycarbonyl or acyl;    Rc=H or alkyl;    Xa,Xb,Xc=O, S, Se, Si(R)2, Te, =C=O, =SO2 or =NRn;    X11,X12=O, S or =NRn;    X21=O, S, =NRn, or bivalent group of formula: =CR201R202;    R201,R202=substituent;    or R201+R202=ring;    ring A=aromatic ring;    ring B=monocyclic or dicyclic aromatic ring or alicyclic ring;    X31,X32=N or =CR31-;    R41,R42=H, formyl, fluoro, chloro, 1-24C alkyl, 2-24C acyl, 3-24C alkoxycarbonyl, 2-24C acyloxy, 1-24C alkylsulfonyl, 1-24C alkoxysulfonyl, nitro, 1-24C perfluoroalkyl, 1-24C perfluoroalkoxy, 1-24C carbamoyl, 1-24C sulfamoyl, 2-24C perfluoroalkyl carbonyl, 2-24C perfluoroalkyl carbonyloxy, 2-24C alkynyl or -CR45=CR46R47;    R45=H or alkyl;    R46,R47=H, cyano, alkoxycarbonyl or acyl, in which one of R46 and R47 is cyano, alkoxycarbonyl or acyl;    R43=substituent;    X41=N or =CR44-;    R,R12,Rn,R31,R44=H or substituent;and    Ya,Yb=halo, perfluoroalkane sulfonyloxy, trialkyl tin group, boronate group or boronic acid group.    when both X31 and X32 are =CR31-, then ring B is monocyclic aromatic ring, alicyclic ring, aromatic ring, or cycloaliphatic monocyclic ring which does not contain nitrogen atom. INDEPENDENT CLAIMS are included for the following:    (1) composition (A), which contains a polymer (a1) having a structural unit of formulae (V)-(VIII) in an organic solvent;    (2) film, which is formed by coating the composition (A); and    (3) organic thin-film solar cell, which consists of primary electrode, secondary electrode, and a photoelectric conversion layer containing the polymer (a1), arranged between the electrodes.    asterisk=bond which forms polymer principal chain.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of the organic thin-film solar cell.    Photoelectric conversion layer (3)    Transparent support (7)    Electrodes (11,12)    P-type semiconductor phase (31)    N-type semiconductor phase (32)