Wave Function Engineering for Efficient Extraction of up to Nineteen Electrons from One CdSe/CdS Quasi-Type II Quantum Dot

Abstract

Solar-to-fuel conversion devices require not only efficient catalysts to accelerate the reactions, but also light harvesting and charge separation components to absorb multiple photons and to deliver multiple electrons/holes to the catalytic centers. In this paper, we show that the spatial distribution of electron and hole wave functions in CdSe/CdS quasi-type II quantum dots enables simultaneous ultrafast charge separation (0.18 ps to adsorbed Methylviologen), ultraslow charge recombination (0.4 μs), and slow multiple-exciton Auger annihilation (biexciton lifetime 440 ps). Up to nineteen excitons per QD can be generated by absorbing multiple 400 nm photons and all excitons can be dissociated with unity yield by electron transfer to adsorbed methylviologen molecules. Our finding demonstrates that (quasi-) type II nanoheterostructures can be engineered to efficiently dissociate multiple excitons and deliver multiple electrons to acceptors, suggesting their potential applications as light harvesting and charge separation components in artificial photosynthetic devices.