Conjugated polymers

A monomer of formula VIa, VIb or VIc

• R7—(Ar1)a—U—(Ar2)c—R8 VIa
• R7—U—(Ar1)a—U—R8 VIb
• R7—U-(Da)a1-(Db)b1-(Dc)c1-(Dd)d1-(De)e1-(Df)f1-R8 VIc
• wherein
• U is a unit of formula I,
• wherein R on each occurrence identically or differently denotes straight-chain or branched alkyl with 16 to 24 C atoms, which is optionally fluorinated.
• Ar1, Ar2 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,
• X0 is halogen,
• a, c are on each occurrence identically or differently 0, 1 or 2,
• Da, Db, Dc, Dd, De and Df are independently of each other aryl or heteroaryl that has electron donor properties and is different from formula I, has 5 to 30 ring atoms, and is optionally substituted by one or more groups RS,
• a1, b1, c1, d1, e1 and f1 are independently of each other 0 or 1, with at least one of a1, b1, c1, d1, e1 and f1 being 1, and
• 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 X0 is halogen, 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.