NOVELTY - A donor-acceptor structural unit-containing compound (M) (I), is new.    USE - New donor-acceptor structural unit-containing compound is used in composition for forming coating film used as semiconductor layer of organic semiconductor device e.g. organic thin film transistor, organic photoelectric conversion device, and thermoelectric conversion device (all claimed) such as hot spring heat generator, waste-heat generator, and solar thermal power generator used in power supply of wristwatch, semiconductor drive, and sensor.    ADVANTAGE - The donor-acceptor structural unit-containing compound has excellent coating characteristics and solubility with respect to organic solvent, and high crystallinity, and enables formation of semiconductor layer with excellent carrier mobility and photoelectric conversion efficiency, which provides organic semiconductor device with reduced variation of threshold voltage.    DETAILED DESCRIPTION - A donor-acceptor structural unit-containing compound (M) of formula (I), is new.    D'=donor structural unit of formula (ii) or (iii) containing alkyl, alkenyl, or alkynyl;    A=acceptor structural unit containing aryl of condensed ring structure in side chain, and alkyl, alkenyl, or alkynyl;    S1,S2=ethenylenyl, ethynylenyl, arylenyl, heteroarylenyl, azo, or -C=N-;    l,n=1-4;    m=0-2;    p=2-2000;    X21,X22=S, O, or -NR22-;    Y21=N, or -C(-L22-R23)= (when X21 and X22 are S);    R21-R23=H or monovalent substituent;    R5=H, alkyl, alkenyl, alkynyl, aryl, or heteroaryl;    X31=S, O, Se, or NR31-;    Y31-Y34=N or -C(-L31-R32)=;    R32=H or monovalent substituent;and    L21,L22,L31=single bond, -O-, -S-, -NR5-, -Si(R5) 2-, -C(=O)O-, -C(=S)O-, -C(=O)S-, -SC(=O)-, -OC(=O)-, -OC(=S)-, -C(=O)-, -C(=S)-, -C(=O)NR5-, -NR5C(=O)-, -S(=O)-, -S(=O)2-, -S(=O)2O-, -OS(=O)2-, -S(=O)2NR5-, -NR5S(=O)2-, arylenyl, heteroarylenyl, alkenylenyl, alkynylenyl, or group which bonds with arylenyl, heteroarylenyl, alkenylenyl, alkynylenyl, carbonyl, or acyloxy.    INDEPENDENT CLAIMS are included for the following:    (1) composition, which contains compound (M) and organic solvent; and    (2) organic semiconductor device, which consists of a semiconductor layer containing the compound (M).