title: Size-dependent trap-assisted Auger recombination in semiconductor nanocrystals.
abstract: The acceleration of Auger-type multicarrier recombination in semiconductor nanocrystals impedes the development of many quantum-dot photonics, solar-cell, lighting, and lasing technologies. To date, only multiexciton and charged-exciton Auger recombination channels are known to show strong size dependence in nanocrystals. Here, we report the first observation of strongly accelerated "trap-assisted" Auger recombination rates in semiconductor nanocrystals. Trap-assisted Auger recombination in ZnO nanocrystals, involving the recombination of conduction-band electrons with deeply trapped holes via nonradiative energy transfer to extra conduction-band electrons, has been probed using time-resolved photoluminescence and transient absorption spectroscopies. We demonstrate that this trap-assisted Auger recombination accelerates dramatically with decreasing nanocrystal size, having recombination times of >1 ns in the largest nanocrystals but only ~80 ps in the smallest. These trap-assisted Auger recombination rates are shown to scale with inverse nanocrystal radius squared (1/τ(Auger) ~ R(-2)). Because surface carrier traps are ubiquitous in colloidal semiconductor nanocrystals, such fast trap-assisted Auger recombination is likely more prevalent in semiconductor nanocrystal photophysics than previously recognized.
authors: Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States.
authors: Alicia W
authors: AW
authors: Cohn
authors: Alina M
authors: AM
authors: Schimpf
authors: Carolyn E
authors: CE
authors: Gunthardt
authors: Daniel R
authors: DR
authors: Gamelin
mesh_terms: D004583:Electrons; D008027:Light; D045663:Quantum Dots / Q000737:chemistry*; D013499:Surface Properties; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D015034:Zinc Oxide