Design of a water-soluble hybrid nanocomposite of CdTe quantum dots and an iridium complex for photoinduced charge transfer

We report the use of an organo-iridium dye conjugated with a water-soluble copolyethylenimine polymer, allowing the hybrid material to be used in combination with thioacid-coated CdTe quantum dots in an aqueous medium. When they are combined, hot carrier cooling observed in the pure quantum-dot case is heavily suppressed indicating fast (ps) electron transfer on a timescale that competes with non-radiative (Auger) relaxation. Fast electron transfer: Picosecond charge transfer between CdTe quantum dots and a novel water-soluble organo-Ir dye is shown. This process allows hot electron transfer from the nanoparticles to the organic component before cooling is complete and before Auger relaxation processes can compete for the carrier's excess energy. Understanding and controlling fast charge transfer is a key to making improved solar-energy conversion devices.