An electroluminescent device, comprising a 2H-benzotriazole compound of the formula wherein Ar 1 and Ar 2 are aryl, which can optionally be substituted, especially C 6 -C 30 aryl, which can optionally be substituted, Y 1 is a divalent linking group selected from the group consisting of especially or especially wherein n2 is 1, 2, or 3, in particular 1, E 1 is -S-, -O-, or -NR 25' -, wherein R 25' is C 1 -C 24 alkyl, or C 6 -C 10 aryl, R 9 and R 10 are independently of each other C 1 -C 24 alkyl, C 1 -C 24 alkyl which is substituted by E and/or interrupted by D, C 6 -C 24 aryl, C 6 -C 24 aryl which is substituted by E, C 2 -C 20 heteroaryl, C 2 -C 20 heteroaryl which is substituted by E, C 2 -C 24 alkenyl, C 2 -C 24 alkynyl, C 1 -C 24 alkoxy, C 1 -C 24 alkoxy which is substituted by E and/or interrupted by D, or C 7 -C 25 aralkyl, or R 9 and R 10 form a ring, especially a five- or six-membered ring, D is -CO-; -COO-; -S-; -SO-; -SO 2 -; -O-; -NR 25 -; -SiR 30 R 31 -; -POR 32 -; -CR 23 =CR 24 -; or -C≡C-; and E is -OR 29; -SR 29; -NR 25 R 26; -COR 28; -COOR 27; -CONR 25 R 26; -CN; -OCOOR 27; or halogen; wherein R 23, R 24, R 25 and R 26 are independently of each other H; C 6 -C 18 aryl; C 6 -C 18 aryl which is substituted by C 1 -C 24 alkyl, or C 1 -C 24 alkoxy; C 1 -C 24 alkyl; or C 1 -C 24 alkyl which is interrupted by -O-; or R 25 and R 26 together form a five- or six-membered ring, in particular R 27 and R 28 are independently of each other H; C 6 -C 18 aryl; C 6 -C 18 aryl which is substituted by C 1 -C 24 alkyl, or C 1 -C 24 alkoxy; C 1 -C 24 alkyl; or C 1 -C 24 alkyl which is interrupted by -O-, R 29 is H; C 6 -C 18 aryl; C 6 -C 18 aryl, which is substituted by C 1 -C 24 alkyl, or C 1 -C 24 alkoxy; C 1 -C 24 alkyl; or C 1 -C 24 alkyl which is interrupted by -O-, R 30 and R 31 are independently of each other C 1 -C 24 alkyl, C 6 -C 18 aryl, or C 6 -C 18 aryl, which is substituted by C 1 -C 24 alkyl, and R 32 is C 1 -C 24 alkyl, C 6 -C 18 aryl, or C 6 -C 18 aryl, which is substituted by C 1 -C 24 alkyl. Ar 1 and Ar 2 are aryl, which can optionally be substituted, especially C 6 -C 30 aryl, which can optionally be substituted, Y 1 is a divalent linking group selected from the group consisting of especially or especially wherein n2 is 1, 2, or 3, in particular 1, E 1 is -S-, -O-, or -NR 25' -, wherein R 25' is C 1 -C 24 alkyl, or C 6 -C 10 aryl, R 9 and R 10 are independently of each other C 1 -C 24 alkyl, C 1 -C 24 alkyl which is substituted by E and/or interrupted by D, C 6 -C 24 aryl, C 6 -C 24 aryl which is substituted by E, C 2 -C 20 heteroaryl, C 2 -C 20 heteroaryl which is substituted by E, C 2 -C 24 alkenyl, C 2 -C 24 alkynyl, C 1 -C 24 alkoxy, C 1 -C 24 alkoxy which is substituted by E and/or interrupted by D, or C 7 -C 25 aralkyl, or R 9 and R 10 form a ring, especially a five- or six-membered ring, D is -CO-; -COO-; -S-; -SO-; -SO 2 -; -O-; -NR 25 -; -SiR 30 R 31 -; -POR 32 -; -CR 23 =CR 24 -; or -C≡C-; and E is -OR 29; -SR 29; -NR 25 R 26; -COR 28; -COOR 27; -CONR 25 R 26; -CN; -OCOOR 27; or halogen; wherein n2 is 1, 2, or 3, in particular 1, E 1 is -S-, -O-, or -NR 25' -, wherein R 25' is C 1 -C 24 alkyl, or C 6 -C 10 aryl, R 9 and R 10 are independently of each other C 1 -C 24 alkyl, C 1 -C 24 alkyl which is substituted by E and/or interrupted by D, C 6 -C 24 aryl, C 6 -C 24 aryl which is substituted by E, C 2 -C 20 heteroaryl, C 2 -C 20 heteroaryl which is substituted by E, C 2 -C 24 alkenyl, C 2 -C 24 alkynyl, C 1 -C 24 alkoxy, C 1 -C 24 alkoxy which is substituted by E and/or interrupted by D, or C 7 -C 25 aralkyl, or R 9 and R 10 form a ring, especially a five- or six-membered ring, D is -CO-; -COO-; -S-; -SO-; -SO 2 -; -O-; -NR 25 -; -SiR 30 R 31 -; -POR 32 -; -CR 23 =CR 24 -; or -C≡C-; and E is -OR 29; -SR 29; -NR 25 R 26; -COR 28; -COOR 27; -CONR 25 R 26; -CN; -OCOOR 27; or halogen; wherein R 23, R 24, R 25 and R 26 are independently of each other H; C 6 -C 18 aryl; C 6 -C 18 aryl which is substituted by C 1 -C 24 alkyl, or C 1 -C 24 alkoxy; C 1 -C 24 alkyl; or C 1 -C 24 alkyl which is interrupted by -O-; or R 25 and R 26 together form a five- or six-membered ring, in particular R 27 and R 28 are independently of each other H; C 6 -C 18 aryl; C 6 -C 18 aryl which is substituted by C 1 -C 24 alkyl, or C 1 -C 24 alkoxy; C 1 -C 24 alkyl; or C 1 -C 24 alkyl which is interrupted by -O-, R 29 is H; C 6 -C 18 aryl; C 6 -C 18 aryl, which is substituted by C 1 -C 24 alkyl, or C 1 -C 24 alkoxy; C 1 -C 24 alkyl; or C 1 -C 24 alkyl which is interrupted by -O-, R 30 and R 31 are independently of each other C 1 -C 24 alkyl, C 6 -C 18 aryl, or C 6 -C 18 aryl, which is substituted by C 1 -C 24 alkyl, and R 32 is C 1 -C 24 alkyl, C 6 -C 18 aryl, or C 6 -C 18 aryl, which is substituted by C 1 -C 24 alkyl.