Effects of solution processing and thermal annealing on the phosphorescence of iridium(III) complex-cored dendrimer films

We present evidence that the photoluminescence (PL) spectrum, PL kinetics and PL efficiency of solution-cast films of a phosphorescent fac-tris(2-phenylpyridyl)iridium(III)-cored dendrimer are not affected by the choice of solvent and thermal annealing. In contrast, when the dendrimer is dispersed into a 4,4′-bis(N-carbazolyl)biphenyl (CBP) host, thermal annealing induces phase separation at a micrometer scale, which results in incomplete energy transfer from CBP to the dendrimer. The insensitivity of the dendrimer film morphology and PL properties to the casting conditions and thermal treatment shows the advantage of host-free electrophosphorescent dendrimers for the further development of light-emitting displays, whilst blended systems are potentially more suitable for photovoltaic applications.