Abstract
Cadmium mercury telluride nanoparticles (CdHgTe NPs) compare multiple exciton generation (MEG) with energy band gap well-suited to the exploitation of the solar spectrum. [Display omitted]
•With well-suited energy band gap for exploitation of the solar spectrum.•A surface trap-free system for ultrafast exciton dynamics.•MEG- significant process of this material.
Ultrafast transient absorption spectroscopy is used to investigate sub-nanosecond exciton dynamics in CdxHg(1−x)Te alloy colloidal quantum dots. A bleach was observed at the band gap due to state-filling, the mono-exponential decay of which had a characteristic lifetime of 91±1ps and was attributed to biexciton recombination; no evidence of surface-related trapping was observed. The rise time of the bleach, which is determined by the rate at which hot electrons cool to the band-edge, ranged between 1 and 5ps depending on the pump photon energy. Measuring the magnitude of the bleach decay for different pump fluences and wavelengths allowed the quantum yield of multiple exciton generation to be determined, and was 115±1% for pump photons with energy equivalent to 2.6 times the band gap.