Materials displaying electron photoemission under visible-light excitation are of great interest for applications in photochemistry, photocathodes, advanced electron beam sources, and electron microscopy. We demonstrate that using CdSe colloidal quantum dots (CQDs) heavily doped with manganese (Mn), we can realize highly efficient electron photoemission under excitation with visible-light pulses. This effect is enabled by extremely fast (&lt;300 femtoseconds) spin-exchange Auger energy transfer from excited Mn ions to an intrinsic CQD exciton. Since the rate of this process outpaces that of intra-band cooling, the high-energy ‘hot’ electron produced by the first Auger-excitation step can be efficiently promoted further into the external ‘vacuum’ state via one more Mn-to-CQD energy-transfer step. This CQD ionization pathway exploits exceptionally large up-hill energy gain rates associated with the spin-exchange Auger process (&gt;10 eV ps<sup>-1</sup>) and leads to photoemission efficiencies of more than 3%, orders of magnitude greater than in the case of undoped CQDs. We demonstrate that using this phenomenon, we can achieve high-yield production of solvated electrons (&gt;3% internal quantum efficiency), which makes it of considerable utility in visible-light-driven   reduction photochemistry.

Advanced photoconversion with magnetically doped quantum dots enabled by ultrafast spin-exchange auger-type interactions

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.