Impact of Postsynthetic Surface Modification on Photoluminescence Intermittency in Formamidinium Lead Bromide Perovskite Nanocrystals

Abstract

We study the origin of photoluminescence (PL) intermittency in formamidinium lead bromide (FAPbBr, FA = HC(NH)) nanocrystals and the impact of postsynthetic surface treatments on the PL intermittency. Single-dot spectroscopy revealed the existence of different individual nanocrystals exhibiting either a blinking (binary on-off switching) or flickering (gradual undulation) behavior of the PL intermittency. Although the PL lifetimes of blinking nanocrystals clearly correlate with the individual absorption cross sections, those of flickering nanocrystals show no correlation with the absorption cross sections. This indicates that flickering has an extrinsic origin, which is in contrast to blinking. We demonstrate that the postsynthetic surface treatment with sodium thiocyanate improves the PL quantum yields and completely suppresses the flickering, while it has no significant effect on the blinking behavior. We conclude that the blinking is caused by Auger recombination of charged excitons, and the flickering is due to a temporal drift of the exciton recombination rate induced by surface-trapped electrons.

Observation of positive and negative trions in organic-inorganic hybrid perovskite nanocrystals

“…The FAPbBr 3 NCs were prepared according to the method described in the literature [42,43]. The procedure is briefly outlined below.…”

Ligand assisted swelling–deswelling microencapsulation (LASDM) for stable, color tunable perovskite–polymer composites

“…The lifetimes of perovskites have been reported before and are dependent on many factors such as excitation power, crystallite size, lm conguration and morphology. [38][39][40][41] A longer lifetime is commonly taken as a sign of better material purity and good passivation of perovskite surfaces. Typically, a smaller particle size is associated with a shorter PL lifetime, due to increased surface areas and likely a larger number of surface defects.…”

Verification of Type-A and Type-B-HC Blinking Mechanisms of Organic–Inorganic Formamidinium Lead Halide Perovskite Quantum Dots by FLID Measurements

“…While the ON state exhibited single exponential distribution corresponding to the lifetime of 23.9 ns, the OFF state could be fitted using a bi-exponential function, which yielded the fast decay time of 2.8 ns followed by a slow component of 19.5 ns. This slow decay lifetime for the OFF state indicated the presence of type-B-HC blinking, where hot electrons might be captured by the RCs before their non-radiative recombination with holes 21 . In addition, Fig.…”

“…Several scholars identified type-A blinking for PQDs using the FLID characteristics and assigned the observed short lifetimes to the trion 13,21,24 . However, the lifetimes of the PQD trion states have been reported to be vastly different, such as 170 ps 21 , 410 ps 28 , 2 ns 24,25 , and 5.8 ns 29 . These values could be comparable with the low-emission state lifetime in type B-BC blinking [23][24][25] .…”