The present invention relates to electroluminescent polymers which comprise 0.01 to 100 mol % of one or more structural units of the formula (I) and/or (II), to a process for the preparation thereof, to blends and formulations comprising these polymers, and to the use of these polymers in electronic devices, in particular in organic light-emitting diodes, so-called OLEDs. The polymers according to the invention exhibit improved efficiency and a longer lifetime, in particular on use in OLEDs.
Conjugated polymers have already been investigated intensively for a long time as highly promising materials in OLEDs. OLEDs which comprise polymers as organic materials are frequently also known as PLEDs (PLED=polymer light-emitting diode). Their simple preparation promises inexpensive production of corresponding light-emitting diodes.
Since PLEDs usually only consist of one light-emitting layer, polymers are required which are able as far as possible to combine all functions (charge injection, charge transport, recombination) of an OLED in themselves. In order to meet these requirements, different monomers which take on the corresponding functions are employed during the polymerisation. Thus, it is generally necessary, for the generation of all three emission colours, to copolymerise certain comonomers into the corresponding polymers (cf., for example, WO 00/46321 A1, WO 03/020790 A2 and WO 02/077060 A1). Thus, it is possible, for example, starting from a blue-emitting base polymer (“backbone”), to generate the other two primary colours red and green.
Various classes of material, such as, for example, poly-para-phenylenes (PPPs), have already been proposed or developed as polymers for full-colour display elements (full-colour displays). Thus, for example, polyfluorene, polyspirobifluorene, polyphenanthrene, polydihydrophenanthrene and polyindenofluorene derivatives come into consideration. Polymers which comprise a combination of the said structural elements have also already been proposed.
The most important criteria of an OLED are efficiency, colour and lifetime. Since these properties are crucially determined by the emitter(s) used, improvements in the emitters compared with the materials known from the prior art continue to be required.
In particular, the lifetime of green- and especially blue-emitting polymers is not yet ideal for many applications. The same applies to the efficiency of red-emitting polymers.
WO 2005/030827 A1 discloses polymers which emit white light. Green-emitting comonomers proposed here are, inter alia, vinylarylene units of the following general formula:

in which Ar is an optionally substituted, aromatic or heteroaromatic ring system. These units should comprise at least one electron-rich ring system Ar or ring system Ar which has electron-rich substituents, such as, for example, thiophene, furan, pyrrole, or phenyl which is substituted by alkoxy, aryloxy or amino groups. The specific examples of WO 2005/030827 A1 disclose a monomer of the following formula:
containing two thiophene-2,5-diyl groups and one 1,4-dialkoxyphenyl group.
With respect to shorter wavelengths, vinylarylene compounds from the prior art only enable the preparation of green emitter units, which in addition exhibit a shift in the emission colour to yellow on use of relatively high concentrations in the polymer. Other colours, especially blue, cannot be achieved with the emitters known from the prior art. In addition, the emitters from the prior art exhibit increased oxidation sensitivity in solution and are therefore difficult to purify.