NOVELTY - A substituted oxepine (I), is new.    USE - New substituted oxepine is used in composition for forming emission layer, electron transport layer and hole blocking layer in electronic device e.g. organic integrated circuit, organic field-effect transistor, organic thin-film transistor, organic solar cell, organic optical detector, organic photoreceptor, and organic electroluminescent device e.g. organic light-emitting transistor, organic field-quench device, organic laser diode, organic light emitting diode and organic light-emitting electrochemical cell e.g. organic light-emitting electrochemical cell, light-emitting electrochemical cell and organic light-emitting electrochemical cell, which are used in phototherapy of skin for preventing or treating psoriasis, atopic dermatitis, jaundice, neonatal jaundice, vitiligo, inflammation and wound healing, and cosmetic for delaying skin aging and treating wrinkles, crow's feet and acne (all claimed).    ADVANTAGE - The substituted oxepine has excellent film forming property and solubility in organic aromatic solvent, and improves durability, operating voltage and efficiency of the electronic device.    DETAILED DESCRIPTION - A substituted oxepine of formula (I), is new.    ring B' condensed with ring A=aryl or heteroaryl, (both optionally substituted with R1);    V'=O, S or C(R4)2;    X=N or CR1;    m=0 (monomer), 1 (dimer) or 2 (trimer);    n=0 or 1;    LK=single bond or bifunctional linker substituted with one or more R1, when m is 1, or trifunctional linker substituted with one or more R1 when m is 2;    R1=e.g. H, D, F, Cl, Br, I, N(R2)2, CN, NO2, Si(R2)3, B(OR2)2, C(=O)R2, P(=O)(R2)2, S(=O)R2, S(=O)2R2, OSO2R2, or 1-40C linear alkyl, alkoxy or thioalkoxy, 2-40C linear alkenyl or alkynyl, 3-40C branched or cyclic alkyl, alkenyl, alkynyl, alkoxy, alkylalkoxy or thioalkoxy (all optionally substituted by one or more R2), or aryl or heteroaryl having 5-60 aromatic ring atoms (both optionally substituted by R2);    R2=e.g. H, D, F, Cl, Br, I, N(R3)2, CN, NO2, Si(R3)3, B(OR3)2, C(=O)R3, P(=O)(R3)2, S(=O)R3, or 1-40C linear alkyl, alkoxy or thioalkoxy, 2-40C linear alkenyl or alkynyl, 3-40C branched or cyclic alkyl, alkenyl, alkynyl, alkoxy, alkylalkoxy or thioalkoxy (all optionally substituted by R3), or aryl or heteroaryl having 5-60 aromatic ring atoms (both optionally substituted by R3), aryloxy, arylalkoxy or heteroaryloxy having 5-60 aromatic ring atoms (all optionally substituted by R3), or diarylamino, diheteroarylamino or aryl-heteroaryl amino having 10-40 aromatic ring atoms (all optionally substituted by R3), in which two or more adjacent R2 form mono or polycyclic, aliphatic or aromatic or heteroaromatic ring system;and    R3=H, D, F or 1-40C aliphatic, aromatic and/or heteroaromatic hydrocarbyl, in which one or several H is optionally substituted by F, and two or more R3 form mono or polycyclic, aliphatic, aromatic or heteroaromatic ring system,    with specified provisos. "Full Definitions are given in the DEFINITIONS (Full Definitions) field ". INDEPENDENT CLAIMS are included for the following:    (1) preparation of substituted oxepine (I);    (2) composition, which comprises compound (I), and additional compound including fluorescent emitter, phosphorescent emitter, host material, matrix material, electron transport material, electron injection material, hole transport material, hole injection material, electron-blocking material, hole blocking material, n-dopant and/or p-dopant;    (3) formulation, which comprises the composition and a solvent;    (4) electronic device, which comprises compound (I) or the composition in an emission layer, an electron transport layer and a hole blocking layer, preferably in emission layer and electron transport layer, more preferably in emission layer; and    (5) production of electronic device, which involves forming an organic layer by vapor deposition or by applying solution.