Picosecond energy transfer and multiexciton transfer outpaces Auger recombination in binary CdSe nanoplatelet solids

Fast fluorescence resonance energy transfer between CdSe nanoplatelets on a picosecond timescale is measured. This process is faster than Auger recombination and leads to the observation of multiexcitonic energy transfer in these materials. Fluorescence resonance energy transfer (FRET) enables photosynthetic light harvesting 1 , wavelength downconversion in light-emitting diodes 2 (LEDs), and optical biosensing schemes 3 . The rate and efficiency of this donor to acceptor transfer of excitation between chromophores dictates the utility of FRET and can unlock new device operation motifs including quantum-funnel solar cells 4 , non-contact chromophore pumping from a proximal LED 5 , and markedly reduced gain thresholds 6 . However, the fastest reported FRET time constants involving spherical quantum dots (0.12–1 ns; refs 7 , 8 , 9 ) do not outpace biexciton Auger recombination (0.01–0.1 ns; ref. 10 ), which impedes multiexciton-driven applications including electrically pumped lasers 11 and carrier-multiplication-enhanced photovoltaics 12 , 13 . Few-monolayer-thick semiconductor nanoplatelets (NPLs) with tens-of-nanometre lateral dimensions 14 exhibit intense optical transitions 14 and hundreds-of-picosecond Auger recombination 15 , 16 , but heretofore lack FRET characterizations. We examine binary CdSe NPL solids and show that interplate FRET (∼6–23 ps, presumably for co-facial arrangements) can occur 15–50 times faster than Auger recombination 15 , 16 and demonstrate multiexcitonic FRET, making such materials ideal candidates for advanced technologies.