Triplet harvesting in poly(9-vinylcarbazole) and poly(9-(2,3-epoxypropyl)carbazole) doped with CdSe/ZnS quantum dots encapsulated with 16-(N-carbazolyl) hexadecanoic acid ligands



Semiconductor quantum dots (QDs) can be used as alternative for transition metal complexes to harvest the nonemissive triplet excitons in organic light-emitting diodes (OLEDs). In search for a QD-based OLED material generating blue emission, poly(9-vinylcarbazole) (PVK) and poly(9-(2,3-epoxypropyl) carbazole) (PEPK) are chosen as host for blue-emitting CdSe/ZnS core/shell QDs. The QDs are encapsulated with 16-(N-carbazolyl) hexadecanoic acid (C16), a ligand terminated by a carbazole moiety. As alternative for PVK, PEPK, where the lower molecular weight and less extensive excimer formation could promise a better film formation and more extensive exciton hopping, is explored. The efficiencies of singlet ( math formula) and triplet ( math formula) energy transfer to the C16 capped QDs are estimated by combining stationary photoluminescence spectra and fluorescence decays of pristine polymer films with those of polymer films doped with the QDs. At a loading of 30 wt % of the QDs, math formula increases from 12 ± 1% in PVK to 41 ± 2% in PEPK while math formula increases from 37 ± 22% in PVK to 72 ± 48% in PEPK. The investigation of the film morphology by atomic force microscopy confirms that the main factor limiting the triplet transfer efficiency in the PVK matrix is the clustering of the C16 capped QDs. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 539–551