Trion Formation Hampers Single Quantum Dot Performance in Silane-Coated FAPbBr 3 Quantum Dots

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Abstract
We explore silane-coated formamidinium lead bromide (FAPbBr3) quantum dots (QDs) as single photon emitters and compare them to FAPbBr3 QDs passivated with a phosphoethylammonium derivative (PEAC8C12), which represents current state-of-the-art ligand passivation. We compare properties including single-photon purity (g(2)(τ)), line width, blinking, and photostability. We find that at room temperature, these silane-coated dots perform comparably to PEAC8C12-passivated dots, while exhibiting improvements in photostability. However, we find that at 4 K, silane-coated FAPbBr3 QDs perform worse than the PEAC8C12-passivated samples, exhibiting faster blue-shifting and photobleaching under illumination. Analysis of fluorescence lifetime intensity distributions from the photon-counting data indicates increased efficiency of fast nonradiative processes in the silane-coated QDs at 4 K. We propose a trion-related degradation pathway at low temperatures that is consistent with the observed kinetics and estimate that at 4 K with 6.1 μJ/cm2, 472 nm excitation the silane-coated QDs build up double the trion population of their PEAC8C12-passivated counterparts.
Funding Information
  • HORIZON EUROPE Marie Sklodowska-Curie Actions (956270)
  • National Science Foundation (DGE 2040434)
  • National Science Foundation (DMR-2019444)

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