TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation (Claimed): An aromatic ring-containing compound (2 equivalent) of formula: Ar1-(A-Ar2)p-Y' is reacted with hydrocarbon compound (1 equivalent) of formula: X-(Ar-A)m-((CH(-R1))h-(Z)i-(CH(-R2))j)k-(A-Ar)n-X, and azomethine oligomer is produced.X=aldehyde or amino group;Ar=optionally substituted bivalent aromatic group;R1,R2=H, 1-20C alkyl, halo or carboxy;Z=bivalent group having oxygen and sulfur, or cycloalkylene group;m,n,i=0 or 1;h,j=0-12;k=1-10;Y',X'=amino or aldehyde;Ar1=optionally substituted monovalent aromatic group;Ar2=optionally substituted bivalent aromatic group;andp=0-5.When Z is oxygen or sulfur, h, and j are 1 or more. Preferred Properties: The azomethine oligomer has molecular weight of 150-15000. The oligomer has solubility of 0.1 g or more with respect to solvent or co-solvent chosen from cresol, toluene, tetrahydrofuran, cyclopentyl methyl ether, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, chloroform, dichloromethane, carbon tetrachloride, chlorobenzene, carbon disulfide, ethyl acetate, butyl acetate, methyl lactate, methanol, ethanol, isopropyl alcohol, benzyl alcohol, n-butanol, t-butanol, pentyl alcohol, ethylene glycol, propylene glycol, propylene glycol monomethyl ether, pyridine, N-methyl pyrrolidone, sulfuric acid, formic acid, acetic acid, hydrochloric acid, lactic acid, triethylamine and dibutyl amine, measured at 25 degrees C. A p-n junction element is produced using azomethine oligomer. A positive electrode terminal is connected to electrode at the side of P-type semiconductor, and a negative electrode terminal is connected to electrode at the side of N-type semiconductor. Voltage of -5 V to +5 V is applied, and electrical energy along reverse direction is set to more than 1 of electrical energy along forward direction. Preferred Compounds: The aromatic ring-containing compound is chosen from 89 compounds e.g. compounds of formulae (I)-(V). The hydrocarbon compound is chosen from 9 compounds e.g. compounds of formulae (VI)-(X). EXAMPLE - Benzaldehyde (in g) (0.85) and m-cresol (10) were added to a nitrogen-substituted tube, and reacted. The reaction solution was heated at 70 degrees C. A diamine component obtained by reacting 1,8-diamino octane (3.57), m-cresol (5) and toluene (30) was dissolved in m-cresol (5), and solution was added. The resulting mixture was stirred for 6 hours, and solvent was removed. The concentrate was vacuum-dried, and azomethine oligomer (0.62) was produced at yield of 55%.