Effects of Halide Composition on the Self-Recovery of Photodegraded Cesium Lead Halide Perovskite Nanocrystals: Implications for Photoluminescence Applications

Abstract

Photodegraded CsPbBr 3 perovskite nanocrystals (NCs) can exhibit complete self-recovery following storage in the dark. This behavior results from the readsorption of surface ligands that experienced photoinduced desorption under UV light excitation. In the present work, mixed-halide CsPb(Cl 0.4 Br 0.6 ) 3 , CsPb-(Cl 0.2 Br 0.8 ) 3 , and CsPb(Br 0.7 I 0.3 ) 3 NCs were prepared via ion exchange to evaluate the influence of halide composition on the photodegradation and self-recovery of NCs. Partially substituting Cl − for Br − enhanced the photoactivation, which improved the photoluminescence properties by optimizing the adsorption state of the surface ligands during light excitation. In contrast, partially substituting I − for Br − reduced the stability of the cubic crystal structure, thus subjecting the NCs to irreversible degradation (likely including a partial phase transition) and preventing their self-recovery. Cycle tests confirmed the reversibility of the photodegradation/self-recovery of CsPbBr 3 NCs; however, this behavior was disturbed by irreversible surface oxidation reactions when the sample was exposed to ambient air. Therefore, it was concluded that ambient air must be excluded to effectively take advantage of the self-recovery phenomenon for practical applications.

Improving the thermal resistance of fluorescent CsPb(Br,I) 3 perovskite quantum dots by surface modification with perfluorodecanoic acid

“…The initial PL intensities before heating are normalized to 100%. A shoulder peak at longer wavelength is observed for the dried film samples, as reported in our previous works [ 32 , 33 , 40 ]. This may be explained by the photon recycling effect [ 41 ].…”

“…Oleic acid (OA) is generally used as a surface ligand in the traditional preparation of CsPbX 3 QDs. However, its desorption from the QDs causes significant degradation of their PL properties [ 32 , 33 ]. The acid dissociation constant (p K a ) of an alkylcarboxylic acid indicates its frequency of deprotonation and thus its adsorptivity as a surface ligand, because carboxylic acids coordinate to crystal surfaces in the deprotonated state.…”

Ligand-modified synthesis of shape-controllable and highly luminescent CsPbBr3 perovskite nanocrystals under ambient conditions

“…In particular, an obvious aggregation could be observed at the low concentration (1.5 mM), which was due to the weak electrostatic repulsion between the nanocrystals binding with the deficient OA ligands. 23 Increasing the OA concentration to 2.0 mM and 2.5 mM, the uniformly dispersed CsPbBr 3 NCs were obtained. As shown in Fig.…”

Highly luminescent perovskite quantum dots for light-emitting devices: photopatternable perovskite quantum dot–polymer nanocomposites

“…From these results, we suspect that the wet-etching step probably led to desorption of the surface ligands, with the PL undergoing self-recovery after re-adsorption of the ligands. 30 The ligand binding to the surface of the PeQDs is highly dynamic and therefore, ligands are easily lost during the wet processes. 30,31 Therefore, the quenching and recovery of the emission could have originated from desorption and re-adsorption of the ligands.…”

“…30 The ligand binding to the surface of the PeQDs is highly dynamic and therefore, ligands are easily lost during the wet processes. 30,31 Therefore, the quenching and recovery of the emission could have originated from desorption and re-adsorption of the ligands. More experiments will have to be performed, however, to confirm the details of the mechanism of this PL recovery.…”