Conjugated polymers, characterised in that they contain 1 to 30 mol% of one or more units of the formula where the symbols and indices used have the following meanings: Ar 1 is on each occurrence, identically or differently, phenyl or phenylene, each of which may be mono- or polysubstituted by R 1, Ar 2 is on each occurrence, identically or differently, phenyl or phenylene, each of which may be mono- or polysubstituted by R 2, Ar 3 is on each occurrence, identically or differently, phenyl or phenylene, each of which may be mono- or polysubstituted by R 3, Ar 4 is on each occurrence, identically or differently, phenylene, 4,4'-biphenylene, 9,9-disubstituted fluorene-2,7-diyl, 6,6,12,12-tetrasubstituted indenofluorene-2,8-diyl or spirobifluorene-2,7-diyl, where these groups may be mono- or polysubstituted by R 5, and R 5 has one of the meanings indicated for R 4, Y is on each occurrence H, R 1-4 are on each occurrence, identically or differently, H, or a hydrocarbon radical having 1 to 40 C atoms, in which, in addition, two or more of the radicals R 1-4 may form an aliphatic or aromatic, mono- or polycyclic ring system with one another, R 1, R 2 and R 3 may also denote a covalent link in the polymer, a is on each occurrence, identically or differently, 1, 2 or 3, b is on each occurrence, identically or differently, 1, 2 or 3, c is on each occurrence, identically or differently, 0 or 1, and further structural units selected from the groups of the fluorenylenes, spirobifluorenylenes, dihydrophenanthrenylenes, tetrahydropyrenylenes, stilbenylenes, bisstyrylarylenes, 1,4-phenylenes, 1,4-naphthylenes, 1,4- or 9,10-anthrylenes, 1,6- or 2,7- or 4,9-pyrenylenes, 3,9- or 3,10-perylenyl-enes, 2,7- or 3,6-phenanthrenylenes, 4,4'-biphenylylenes, 4,4"-ter-phenylylenes or 4,4'-bis-1,1'-naphthylylenes, selected from the groups of the triarylamines, triarylphosphines, benzidines, tetraarylene-para-phenylenediamines, phenothiazines, phenoxazines, dihydrophenazines, thianthrenes, dibenzo-p-dioxins, phenoxathiynes, carbazoles, azulenes, thiophenes, pyrroles or furans, and/or selected from the groups of the pyridines, pyrimidines, pyridazines, pyrazines, anthracenes, triarylboranes, oxadiazoles, quinolines, quinoxalines or phenazines. Ar 1 is on each occurrence, identically or differently, phenyl or phenylene, each of which may be mono- or polysubstituted by R 1, Ar 2 is on each occurrence, identically or differently, phenyl or phenylene, each of which may be mono- or polysubstituted by R 2, Ar 3 is on each occurrence, identically or differently, phenyl or phenylene, each of which may be mono- or polysubstituted by R 3, Ar 4 is on each occurrence, identically or differently, phenylene, 4,4'-biphenylene, 9,9-disubstituted fluorene-2,7-diyl, 6,6,12,12-tetrasubstituted indenofluorene-2,8-diyl or spirobifluorene-2,7-diyl, where these groups may be mono- or polysubstituted by R 5, and R 5 has one of the meanings indicated for R 4, Y is on each occurrence H, R 1-4 are on each occurrence, identically or differently, H, or a hydrocarbon radical having 1 to 40 C atoms, in which, in addition, two or more of the radicals R 1-4 may form an aliphatic or aromatic, mono- or polycyclic ring system with one another, R 1, R 2 and R 3 may also denote a covalent link in the polymer, a is on each occurrence, identically or differently, 1, 2 or 3, b is on each occurrence, identically or differently, 1, 2 or 3, c is on each occurrence, identically or differently, 0 or 1,