Complete self-recovery of photoluminescence of photodegraded cesium lead bromide quantum dots

Abstract

Self-readsorption of surface ligands completely restores the photoluminescence of CsPbBr3 quantum dots damaged by excitation light.

Implications of gas-barrier properties in realizing the self-recovery of photodegraded CsPbBr3 perovskite nanocrystals

“…These color changes are attributed to the photoinduced desorption and readsorption of surface ligands on the NCs. 42 Conversely, the EVA-coated film changes from yellow to orange, as also observed for the reference film, which is exposed to ambient air. The film cannot recover its color, even upon subsequent dark storage for 168 h. The UV-vis spectra of the reference and EVA-coated films also exhibit similar changes during irradiation and dark storage.…”

“…The present authors previously reported that, after significant photodegradation by light excitation, solid CsPbBr 3 NCs sealed with a glass plate exhibit complete self-recovery of PL properties. 42 In that study, the PL intensity of the NCs decreased to B20% of the initial intensity under 72 h blue LED irradiation, but then spontaneously increased to 108% upon subsequent dark storage for 2400 h. The solid sample changed from yellow to black during irradiation owing to photoinduced desorption of the surface ligands, but the yellow color was restored after dark storage. We concluded that self-recovery occurs when the desorbed surface ligands are readsorbed during dark storage.…”

Direct Observation of Shallow Trap States in Thermal Equilibrium with Band‐Edge Excitons in Strongly Confined CsPbBr3 Perovskite Nanoplatelets

“…The number a is proportional to the number of NPls with ligands desorbed from their surface. [23][24][25]41,42] The FLUPS signal intensity is only proportional to X 1 and X 1 ′ population while the GSB intensity in TA follows the population of X 1 , X 1 ′, and S since these states are close by in energy (Equations (5) and (6)). Deep traps states are usually located in the middle of the band gap and do not contribute to the GSB signal in TA, leading to a bi-expontential decay behavior for the GSB, where the fastest decay lifetime is associated with the unreversible trapping into the D-state and the longest lifetime corresponds to the radiative recombination of band-edge excitons.…”

“…[20][21][22][23][24][25] Over time, ligands are removed from the surface, leaving undercoordinated Br or Pb atoms that act as deep trap states. [41,42] These deep traps reduce the proportion of excitons emitting radiatively and thus reduce the PLQY.…”

Exploring the physics of cesium lead halide perovskite quantum dots via Bayesian inference of the photoluminescence spectra in automated experiment

“…It appears that these QDs cannot be formed until about an hour in ambient conditions. This could be due to the solid solution between iodide-and bromide-based perovskites cannot initially form stable QDs but throughout time the bromide helps stabilizes the QDs based on their environment [29]. Since CsPbI 3 tends to be the most unstable in ambient conditions, it is surprising that the PL peaks get more intense as time goes on [24].…”