A polymer of formula or wherein x = 0.70 to 0.99, y = 0.30 to 0.01, and wherein x + y = 1, r + s = 0.50 to 0.99, t + u = 0.50 to 0.01, and wherein r + s + t + u = 1, A is a group of formula wherein R 1 and R 2 may be the same or different and are selected from hydrogen, a C 1 -C 38 alkyl group, a C 2 -C 38 alkenyl group, a C 3 -C 38 alkinyl group, each of which can optionally be interrupted one or more times by -O-, -S- or COO, a C 7 -C 100 arylalkyl group, which can be substituted one to five times with C 1 -C 8 alkyl, C 1 -C 8 alkoxy, CF 3 and/or F; and a phenyl group which can optionally be substituted one or more times by C 1 -C 25 alkyl, C 1 -C 8 alkoxy, halogen or cyano; Ar 1 and Ar 2 are independently of each other a group of formula B is a group of formula III, which is different from A, D has the meaning of Ar 1, or is a group of formula R 204 and R 205 are independently of each other H, CN, COOR 206 or C 1 -C 8 alkyl; R 206 is a C 1 -C 18 alkyl group; E is a group of formula which is different from D, wherein k is 1, l is 0, or 1, v is 0, or 1, z is 0, or 1, a is an integer of 1 to 5, Ar 4, Ar 5, Ar 6 and Ar 7 are independently of each other a group of formula wherein one of X 5 and X 6 is N and the other is CR 14, Ar 20 is an arylene group, or a heteroarylene group, each of which may optionally be substituted, R 12 and R 12' are independently of each other hydrogen, halogen, C 1 -C 25 alkyl, which may optionally be interrupted by one, or more oxygen, or sulphur atoms, C 1 -C 25 alkoxy, C 7 -C 25 arylalkyl, or R 13, R 13 is a C 1 -C 8 alkyl group, or a tri(C 1 -C 8 alkyl)silyl group, R 14, R 14', R 15, R 15', R 17 and R 17' are independently of each other H, or a C 1 -C 25 alkyl group, which may optionally be interrupted by one or more oxygen atoms; R 18 and R 18' independently of each other hydrogen, halogen, C 1 -C 25 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms, C 7 -C 25 aralkyl, or C 1 -C 25 alkoxy; R 19 is hydrogen, C 7 -C 25 aralkyl, C 6 -C 18 aryl; C 6 -C 18 aryl which is substituted by C 1 -C 18 alkyl, or C 1 -C 18 alkoxy; or C 1 -C 25 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms; R 20 and R 20' are independently of each other hydrogen, C 7 -C 25 aralkyl, C 1 -C 25 alkyl, which may optionally be interrupted by one, or more oxygen, or sulphur atoms, X 7 is -O-, -S-, -NR 115 -, -Si(R 117)(R 117')-, -C(R 120)(R 120)-, -C(=O)-, X 8 is -O-, or -NR 115 -; R 100 and R 100' are independently of each other H, F, C 1 -C 18 alkyl, C 1 -C 18 alkyl which is interrupted by O, C 1 -C 18 alkoxy, C 1 -C 18 alkoxy which is interrupted by O, C 1 -C 18 perfluoroalkyl, C 6 -C 24 aryl, which may optionally be substituted one to three times with C 1 -C 8 alkyl and/or C 1 -C 8 alkoxy, C 2 -C 20 heteroaryl, which may optionally be substituted one to three times with C 1 -C 8 alkyl and/or C 1 -C 8 alkoxy; R 101 and R 101' are independently of each other H, F, C 1 -C 18 alkyl, C 1 -C 18 alkyl which is interrupted by O, C 1 -C 18 alkoxy, C 1 -C 18 alkoxy which is interrupted by O, C 1 -C 18 perfluoroalkyl, C 6 -C 24 aryl, which may optionally be substituted one to three times with C 1 -C 8 alkyl and/or C 1 -C 8 alkoxy, C 2 -C 20 heteroaryl, which may optionally be substituted one to three times with C 1 -C 8 alkyl and/or C 1 -C 8 alkoxy; R 102 and R 102' are independently of each other H, halogen, C 1 -C 25 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms; C 7 -C 25 arylalkyl, or C 1 -C 25 alkoxy; R 103 and R 103' are independently of each other hydrogen, halogen, C 1 -C 25 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms; C 6 -C 24 aryl, which may optionally be substituted one to three times with C 1 -C 8 alkyl and/or C 1 -C 8 alkoxy; C 7 -C 25 arylalkyl, CN, or C 1 -C 25 alkoxy; or R 103 and R 103' together form a ring, R 115 and R 115' are independently of each other hydrogen, C 6 -C 18 aryl; C 6 -C 18 aryl which is substituted by C 1 -C 18 alkyl, or C 1 -C 18 alkoxy; C 1 -C 25 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms; or C 7 -C 25 arylalkyl, R 116 is hydrogen, C 7 -C 25 arylalkyl, C 6 -C 18 aryl; C 6 -C 18 aryl which is substituted by C 1 -C 18 alkyl, C 1 -C 18 perfluoroalkyl, or C 1 -C 18 alkoxy; C 1 -C 25 alkyl; C 1 -C 25 alkyl which is interrupted by -O-, or-S-; or -COOR 119; R 119 is C 1 -C 38 alkyl; R 117 and R 117' are independently of each other C 1 -C 35 alkyl group, C 7 -C 25 arylalkyl, or a phenyl group, which optionally can be substituted one to three times with C 1 -C 8 alkyl and/or C 1 -C 8 alkoxy, R 120 and R 120' are independently of each other hydrogen, C 1 -C 38 alkyl, which may optionally be interrupted by one, or more oxygen, or sulphur atoms; or C 7 -C 25 arylalkyl, and R 121 is H, C 1 -C 18 alkyl, which may optionally be interrupted by one or more oxygen or sulphur atoms, C 1 -C 18 perfluoroalkyl, C 6 -C 24 aryl, which may optionally be substituted one to three times with C 1 -C 8 alkyl and/or C 1 -C 8 alkoxy; C 2 -C 20 heteroaryl, which may optionally be substituted one to three times with C 1 -C 8 alkyl and/or C 1 -C 8 alkoxy; or CN.