Self-Assembled Core-Shell CdTe/Poly(3-hexylthiophene) Nanoensembles as Novel Donor-Acceptor Light-Harvesting Systems

The self-assembly of novel core-shell nanoensembles consisting of regioregular poly(3-hexylthiophene) nanoparticles (P3HT_NPs) of 100 nm as core and semiconducting CdTe quantum dots (CdTe_QDs) as shell with a thickness of a few tens of nanometers was accomplished by employing a reprecipitation approach. The structure, morphology, and composition of CdTe_QDs/P3HT_NPs nanoensembles were confirmed by high-resolution scanning transmission microscopy and dynamic light-scattering studies. Intimate interface contact between the CdTe_QDs shell and the P3HT_NPs core leads to the stabilization of the CdTe_QDs/P3HT_NPs nanoensemble as probed by the steady-state absorption spectroscopy. Effective quenching of the characteristic photoluminescence of CdTe_QDs at 555 nm, accompanied by simultaneous increase in emission of P3HT_NPs at 660 and 720 nm, reveals photoinduced charge-transfer processes. Probing the redox properties of films of CdTe_QDs/P3HT_NPs further proves the formation of a stabilized core-shell system in the solid state. Photoelectrochemical assays on CdTe_QDs/P3HT_NPs films show a reversible on-off photoresponse at a bias voltage of +0.8 V with a 3 times increased photocurrent compared to CdTe_QDs. The improved charge separation is directly related to the unique core-shell configuration, in which the outer CdTe_QDs shell forces the P3HT_NPs core to effectively act as electron acceptor. The creation of novel donor-acceptor core-shell hybrid materials via self-assembly is transferable to other types of conjugated polymers and semiconducting nanoparticles. This work, therefore, opens new pathways for the design of improved optoelectronic devices.