Conjugated polymers

A monomer of formula VIa or VIb

• R7—(Ar1)a-U-(Ar2)c—R8 VIa
• R7-U-(Ar1)a-U-R8 VIb
• wherein a and c are identically or differently 0, 1 or 2,
• U is a unit of formula I,
• wherein the individual radicals have the following meanings:
• X and Y independently of each other, and on each occurrence identically or differently, C(R1R2), C=C(R1R2), Si(R1R2), Ge(R1R2), C(=O) or NR1,
• A1
• A2 on each occurrence identically or differently
• A3 on each occurrence identically or differently
• Provided that A1, A2 and A3 do not at the same time denote a benzene ring,
• V CR1 or N,
• W O, S or Se,
• R1 and R2 independently of each other H, straight-chain, branched or cyclic alkyl with 1 to 30 C atoms, in which one or more CH2 groups are optionally replaced by —O—, —S—, —C(=O)—, —C(=S)—, —(C=O)—O—, —O—C(=O)—, —NR0—, SiR0R00—, —CF2—, —CHR0=CR00—, —CY1=CY2— or —C≡C— in such a manner that O and/or S atoms are not linked directly to one another, and in which one or more H atoms are optionally replaced by F, Cl, Br, I or CN, or denote aryl, heteroaryl, aryloxy or heteroaryloxy with 4 to 20 ring atoms which is optionally substituted,
• Y1 and Y2 independently of each other H, F, Cl or CN,
• Ar1, Ar2, Ar3 are, on each occurrence identically or differently, and independently of each other, aryl or heteroaryl that is different from U has 5 to 30 ring atoms and is optionally substituted by one or more groups RS,
• RS is on each occurrence identically or differently F, Br, Cl, —CN, —NC, —NCO, —NCS, —OCN, —SCN, —C(O)NR0R00, —C(O)X0, —C(O)R0, —NH2, —NR0R00, —SH, —SR0, —SO3H, —SO2R0, —OH, —NO2, —CF3, —SF5, optionally substituted silyl, carbyl or hydrocarbyl with 1 to 40 C atoms that is optionally substituted and optionally comprises one or more hetero atoms,
• R0 and R00 are independently of each other H or optionally substituted C1-40 carbyl or hydrocarbyl,
• R7 and R8 are selected from the group consisting of Cl, Br, I, O-tosylate, O-triflate, O-mesylate, O-nonaflate, —SiMe2F, —SiMeF2, —O—SO2Z1, —B(OZ2)2, —CZ3═C(Z3)2, —C≡CH, —C≡CSi(Z1)3, —ZnX0 and —Sn(Z4)3, wherein X° is halogen, and
• Z1-4 are selected from the group consisting of alkyl and aryl, each being optionally substituted, and two groups Z2 may also together form a cyclic group.