Fabrication of quantum dot-polymer composites: Semiconductor nanoclusters in dual-function polymer matrices with electron-transporting and cluster-passivating properties

Hybrid inorganic-organic polymer composites have been prepared by a convergent approach in which nearly monodisperse CdSe or(CdSe)ZnS nanoclusters are sequestered within phosphine-containing domains in a charge-transporting matrix. The motivation for these studies is the potential utility of such composites as combined electron-transport and emitter layers in light-emitting devices. Diblock copolymers with electronically passivating and charge-transport capabilities were prepared via ring-opening metathesis polymerization of octylphosphine- and oxadiazole-functionalized norbornenes. Independently prepared CdSe and ZnS-overcoated CdSe nanoclusters, surface-passivated by trioctylphosphine and trioctylphosphine oxide groups, are tethered by polymer-bound phosphine donors, resulting in immediate, sustained increases in fluorescence. Thin films of the CdSe-block copolymer composites, static-cast from dilute solution, exhibit microphase separation, with segregation of nanoclusters within phosphine-rich microdomains. Under similar conditions, (CdSe)ZnS clusters undergo macrophase separation. Rapid-casting techniques arrest morphological development at an earlier stage, giving small micelles of a few nanoclusters each in phosphine-containing domains. Dispersion of electronically passivated nanoclusters throughout a functionalized polymer matrix leads to composites with a broad range of potential applications, including light-emitting devices and photovoltaic cells.