NOVELTY - Polymer comprising substituted dibenzo-cycloheptane structural units (I), is new.    USE - The polymer or the mixture is useful in at least one active layer of an organic electronic device, preferably an organic electroluminescent device (organic light-emitting diode) (preferred), organic light-emitting electrochemical cell, organic integrated circuit, organic field-effect transistor, organic thin-film transistor, organic solar cell, organic laser diode, organic photovoltaic element or organic photovoltaic device and an organic photoreceptor (all claimed).    ADVANTAGE - The polymer exhibits large band gap, which achieves a deeper blue singlet emission for display applications with large color space, increases service life, efficiency and quality of the organic electroluminescent devices.    DETAILED DESCRIPTION - Polymer comprising substituted dibenzo-cycloheptane structural units of formula (I), is new.    R1, R2 = 1-40C alkyl, 1-40C alkoxy or 1-40C thioalkoxy (all optionally branched or cyclic, and in all groups at least one H is optionally replaced by F, and at least one non-adjacent CH2 is optionally replaced by O, S Si(R3)2, Ge(R3)2, BR3, NR3, PR3, CO, C=S, C=Se, C=NR3, PO(R3), PS(R3), R3C=CR3, CC, SO, SO2, COO, O(CO)O or CONR3), H, D, F, OH, N(R3)2 or mono- or polycyclic and (hetero)aromatic ring;    R3 = 1-40C alkyl, 1-40C alkoxy or 1-40C thioalkoxy (all optionally branched or cyclic, and in all groups at least one H is optionally replaced by F, and at least one non-adjacent CH2 is optionally replaced by O, CO, COO or O(CO)O), H, F or mono- or polycyclic and (hetero)aromatic ring; and    m, n = 0-3, preferably 0.    INDEPENDENT CLAIMS are also included for:    (1) substituted dibenzo-cycloheptane compounds of formula (II);    (2) a mixture comprising the above polymer and additionally polymeric-, oligomeric-, dendritic- or low molecular weight substances; and    (3) a formulation comprising the polymer and at least one solvent.    X = leaving group suitable for polymerization reaction.