Conjugated polymer selected from formulae IVd and IVe *-[(Ar 1) a - b -(Ar 2) c -(Ar 3) d] n -* IVd *-([(Ar 1) a - b -(Ar 2) c -(Ar 3) d] x -[(Ar 1) a -(A 1) b -(Ar 2) c -(Ar 3) d] y) n -* IVe wherein U is a unit of formula I, wherein V 1 and V 2 are S, X 1 and X 2 are independently of each other CR 1 R 2, R 1 and R 2 independently of each other denote straight-chain, branched or cyclic alkyl with 1 to 20 C atoms which is unsubstituted or substituted by one or more F atoms, or R 1 and R 2 independently of each other denote aryl or heteroaryl, each of which is optionally fluorinated, alkylated or alkoxylated and has 4 to 30 ring atoms, or one of R 1 and R 2 denotes H and the other is selected from the aforementioned alkyl, aryl or heteroaryl groups, or R 1 and R 2 together form a cyclic alkyl group with 1 to 20 C atoms, which is unsubsituted or substituted by one or more F atoms or by one or more C 1 -C 10 alkyl groups, R denotes H, Ar 1, Ar 2, Ar 3 are, on each occurrence identically or differently, and independently of each other, aryl or heteroaryl that is different from U, preferably has 5 to 30 ring atoms and is optionally substituted, preferably by one or more groups R S, R S is on each occurrence identically or differently F, Br, Cl, -CN, -NC, -NCO, -NCS, -OCN, -SCN, -C NR 0 R 00,-C X 0, -C R 0, -NH 2, -NR 0 R 00, -SH, -SR 0, -SO 3 H,-SO 2 R 0, -OH, -NO 2, -CF 3, -SF 5, optionally substituted silyl, carbyl or hydrocarbyl with 1 to 40 C atoms that is optionally substituted and optionally comprises one or more hetero atoms, R 0 and R 00 are independently of each other H or optionally substituted C 1-40 carbyl or hydrocarbyl, X 0 is halogen, preferably F, Cl or Br, a, b, c are on each occurrence identically or differently 0, 1 or 2, d is on each occurrence identically or differently 0 or an integer from 1 to 10, A 1 is an aryl or heteroaryl group that is different from U and Ar 1-3, has 5 to 30 ring atoms, is optionally substituted by one or more groups R S, and is selected from aryl or heteroaryl groups having electron acceptor properties, x is > 0 and ≤ 1, y is ≥ 0 and < 1, x + y is 1, and n is an integer >1. wherein the polymer is an alternating or random copolymer, and wherein in formula IVd and IVe in at least one of the repeating units [(Ar 1) a - b -(Ar 2) c -(Ar 3) d] and in at least one of the repeating units [(Ar 1) a -(A 1) b -(Ar 2)c - (Ar 3) d] b is at least 1. U is a unit of formula I, V 1 and V 2 are S, X 1 and X 2 are independently of each other CR 1 R 2, R 1 and R 2 independently of each other denote straight-chain, branched or cyclic alkyl with 1 to 20 C atoms which is unsubstituted or substituted by one or more F atoms, or R 1 and R 2 independently of each other denote aryl or heteroaryl, each of which is optionally fluorinated, alkylated or alkoxylated and has 4 to 30 ring atoms, or one of R 1 and R 2 denotes H and the other is selected from the aforementioned alkyl, aryl or heteroaryl groups, or R 1 and R 2 together form a cyclic alkyl group with 1 to 20 C atoms, which is unsubsituted or substituted by one or more F atoms or by one or more C 1 -C 10 alkyl groups, R denotes H, Ar 1, Ar 2, Ar 3 are, on each occurrence identically or differently, and independently of each other, aryl or heteroaryl that is different from U, preferably has 5 to 30 ring atoms and is optionally substituted, preferably by one or more groups R S, R S is on each occurrence identically or differently F, Br, Cl, -CN, -NC, -NCO, -NCS, -OCN, -SCN, -C NR 0 R 00,-C X 0, -C R 0, -NH 2, -NR 0 R 00, -SH, -SR 0, -SO 3 H,-SO 2 R 0, -OH, -NO 2, -CF 3, -SF 5, optionally substituted silyl, carbyl or hydrocarbyl with 1 to 40 C atoms that is optionally substituted and optionally comprises one or more hetero atoms, R 0 and R 00 are independently of each other H or optionally substituted C 1-40 carbyl or hydrocarbyl, X 0 is halogen, preferably F, Cl or Br, a, b, c are on each occurrence identically or differently 0, 1 or 2, d is on each occurrence identically or differently 0 or an integer from 1 to 10, x is > 0 and ≤ 1, y is ≥ 0 and < 1, x + y is 1, and n is an integer >1.