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

We explore silane-coated formamidinium lead bromide (FAPbBr 3 ) quantum dots (QDs) as single photon emitters and compare them to FAPbBr 3 QDs passivated with a phosphoethylammonium derivative (PEAC 8 C 12 ), 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 PEAC 8 C 12 -passivated dots, while exhibiting improvements in photostability. However, we find that at 4 K, silane-coated FAPbBr 3 QDs perform worse than the PEAC 8 C 12 -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/cm 2, 472 nm excitation the silane-coated QDs build up double the trion population of their PEAC 8 C 12 -passivated counterparts.