Patent ID: 8124248

Claim:
A polymer blend comprising a first, light-emissive polymer comprising substituted or non-substituted units according to formulae (I) and (II), and a second, hole transport polymer consisting of alternating single repeat units (a) and (b), said single repeat unit (a) comprising a substituted or non-substituted fluorene unit according to formula (I) and said single repeat unit (b) comprising a substituted or non-substituted triarylamine unit, wherein the molecular weights of the first and second polymers and the blending ratio of the first and second polymers are selected such that, in use in a light-emissive device, the luminance of the emitted light at a bias of 5V is no less than 20,000 cd/m 2 wherein R′ is independently in each occurrence H, C 1 -C 20 hydrocarbyl or C 1 -C 20 hydrocarbyl containing one or more S, N, O, P or Si atoms, C 4 -C 16 hydrocarbyl carbonyloxy, C 4 -C 16 aryl(trialkylsiloxy) or both R′ may form together with the 9-carbon on the fluorene ring a C 5 -C 20 cyclic structure optionally containing one or more heteroatoms of S, N or O, the proportion of the first polymer in the polymer blend is at least 70 weight percent, and the triarylamine units of the second polymer include one or more types of triarylamine units selected from the group consisting of those according to the following formulae (IV), (V), and (VI):