End-Functionalized Semiconducting Polymers as Reagents in the Synthesis of Hybrid II-VI Nanoparticles

The functionalization of II-VI nanocrystals with semiconducting polymers is of fundamental interest for lightweight, solution-processed optoelectronics. The direct surface functionalization of nanocrystals is useful for facilitating charge transfer across the donor/acceptor interface, in addition to promoting good mixing properties and thereby helping prevent nanoparticle aggregation. In this work, we develop a new method for the direct attachment of semiconducting polymers to II-VI inorganic nanocrystals, where the polymer plays a dual role, acting as both the desired capping agent and a chalcogenide monomer during synthesis. The success of this hybridization procedure relies on the establishment of a new polymer end-functionalization scheme, where a route toward a thio-phosphonate polymer end-group is developed; this end-group resembles many chalcogenide precursor materials used in the synthesis of II-VI nanomaterials. We show the applicability of this hybrid functionalization procedure by attaching poly(3-hexylthiophene-2,5-diyl) to CdSe and CdS. We followed the progress of the reaction by NMR and used transmission electron microscopy to determine the morphology of the resulting materials, which we found to have narrow size distributions after hybridization. Polymer attachment to the nanocrystals was confirmed by examining the steady-state and time-resolved optical properties of the hybrid materials, which also provided an insight into excited-state processes occurring across the hybrid interface.