NOVELTY - A thin film comprises an organic compound (I) containing bismuth in structure skeleton.    USE - Thin film is used in various elements (claimed) used as switching element, photoelectric conversion element, or optical wavelength conversion switch element. Uses include but are not limited to organic electroluminescent elements, organic solar cells, organic transistors, display elements used in display apparatus of computers, televisions, portable terminals, mobile telephones, and video cameras, planar light-emitting elements used as planar light source for backlights of LCD devices and illumination. Can also be used as charge transport material, electric charge injection material, electroconductive material, synthetic raw material of compounds, additive, modifier, chemical agent, and sensor.    ADVANTAGE - The thin film has excellent light-emission property as bismuth which has the heaviest isotope which may exist stably on a periodic table is included. Since bismuth is low-toxic, the thin film is environmentally-friendly. The thin film can be formed easily with uniform thickness.    DETAILED DESCRIPTION - A thin film comprises an organic compound of formula (I) containing bismuth in structure skeleton.    Ar1,Ar2=3-30C aromatic ring;    R1,R2=substituent;    a,b=0-12;    two R1 groups,two R2 groups=ring structure unitedly;    A1=direct bond, -O-, -S-, -S(=O)-, -S(=O)2-, -PR3-, -NR4-, or -C(-R5)2-;    R3-R5=H or substituent;    E1=50C or less monovalent group;    L1=50C or less ligand;    c=0-3;    E1+Ar1,E1+Ar2=bond;and    L1+E1, L1+Ar1,L1+Ar2,each combination of L1=bond, when c is 1-3.    INDEPENDENT CLAIMS are included for the following:    (1) composition comprising compound (I) and an organic solvent;    (2) organic compound of formula (II or III) containing bismuth in structure skeleton; and    (3) compound including a structural unit consisting of a structure obtained by removing hydrogen atom(s) from compound (I), and having a number average molecular weight of 103-107 by polystyrene conversion.    R8=substituent;    d=0-5;    R8 groups=bond;    any two of X7-X9=-CR9=, with the remaining being -S-;    two of X10-X12=-CR9=, with the remaining being -S-;    R9=H or substituent chosen from optionally substituted hydrocarbyl, optionally substituted hydrocarbyloxy, and optionally substituted silyl, with at least one R9 being substituent;    adjacent R9 groups=bond;    a',b'=0-4;and    n'=1 or 2.