Recently it was proposed that using hybrid polymer/inorganic nanoparticles (NPs) as an active layer in hybrid light emitting diodes (LEDs) leads to improved charge injection balance compared to devices with only NPs [1]. In this work, hybrids containing CdSe@ZnS quantum dots (QDs) and carbazole-based polymers have been investigated as an active layer in hybrid LEDs. Multiple carbazole based monomers have been synthesized and have been further polymerized via radical addition fragmentation chain transfer (RAFT) polymerization to yield side-chain conjugated polymers. The resulting polymers exhibit different electrochemical as well as optical properties. The properties are dependent on the side groups attached to the carbazole functionality of the monomer. Furthermore, to achieve better dispersion of the QDs in the polymer matrix anchoring disulfide groups, which can graft to the surface of QDs, have been incorporated into the polymer. To achieve this perfluorophenyl reactive ester moieties were incorporated into the polymers either as a single end group or as a second block. Thereafter, through post polymerization modification reactions the reactive ester groups were replaced with disulfide containing functionalities. Finally, the polymer-functionalized QDs were examined as the active layer in LEDs. Various device configurations have been tested to determine the QD excitation mechanism in our hybrid systems. Direct charge injection from the surrounding polymer matrix into a QD as well as energy transfer from the polymer to the QDs has been investigated.
[1] W. K. Bae, J. Lim, M. Zorn, J. Kwak, Y.S. Park, D. Lee, S. Lee, K. Char, R. Zentel, C. Lee, J. Mat. Chem. C, 2014, 2, 4974