The Degradation and Blinking of Single CsPbI₃ Perovskite Quantum Dots

Abstract

We demonstrate using single molecule spectroscopy that inorganic CsPbI3 perovskite quantum dots (PQDs) undergo an irreversible, photoaccelerated reaction with water that results in a blue-shift of the photoluminescence (PL) and ultimately to complete quenching of the emission. We find that decomposition does not take place in the presence of oxygen alone but that it requires light and water. We also analyze the blinking for some stable PQDs and find a continuous distribution of emission states with a linear correlation between intensity and lifetime. We postulate that, in addition to charging and discharging processes, blinking arises from the activation and deactivation of nonradiative recombination centers in the PQDs.

Excitation Intensity Dependence of Photoluminescence Blinking in CsPbBr3 Perovskite Nanocrystals

“…Previous studies of lead halide perovskite NCs have observed photodegradation with an accompanying dynamical blueshift, attributed to a core-size reduction from surface destruction. 33,42 The measurements in this experiment were performed with a PMMA polymer encapsulation layer coated over the isolated CsPbBr 3 NCs, which is expected to act as a hydrophobic barrier and provide protection from water. 43 Thus, photodegradation at the highest intensities is expected to be caused by the opening of new, nonradiative sites as opposed to a waterassisted surface destruction.…”

Unveiling the Photo‐ and Thermal‐Stability of Cesium Lead Halide Perovskite Nanocrystals

“…CsPbCl 3 and CsPbBr 3 nanocrystals are reported to be stable in the cubic phase, while CsPbI 3 slowly reverts to the thermodynamically-favored δ-phase, which is yellow. [54] For films in air, photobrightening followed by photodegradation was observed under illumination, and degradation is also observed for films in dark, ambient conditions. [59] Importantly, the δ phase for CsPbI 3 is nonluminescent, rendering the material unusable for most applications.…”

“…Yuan et al demonstrated that CsPbI 3 nanocrystals undergo irreversible photodegradation that quenches the photoluminescence under light irradiation. [54] For films in air, photobrightening followed by photodegradation was observed under illumination, and degradation is also observed for films in dark, ambient conditions. Additionally, several groups have been developing methods of protecting the perovskite structure from moisture, including overlaying silicone resins, [60] preparing polymer or related composites, [61][62][63] and coating with zwitterion [64] or metal complexes.…”

“…[15] Other syntheses have expanded this general idea by generating multiple nanocrystal morphologies through ligand mediation [21][22] and reaction tuning, [23] by using different surface ligands for improved quantum yields, [24][25] by increasing surface passivation/repair via salt solutions, [26][27][28][29] as well as by generating other cation/anion compositions through doping [17,[30][31][32][33][34][35] or post-synthetic ion exchange. [51][52][53][54] Park et al observed strong photon antibunching as well as blinking behavior ascribed to charge/discharge events triggered by photoionization in CsPbBr 3 and CsPbI 3 . [26,40] The photophysics of MAPbX 3 nanocrystals have been extensively studied, [41][42][43][44][45][46][47][48][49][50] and there are several reports on various luminescence properties of CsPbX 3 .…”

“…[26,40] The photophysics of MAPbX 3 nanocrystals have been extensively studied, [41][42][43][44][45][46][47][48][49][50] and there are several reports on various luminescence properties of CsPbX 3 . [51][52][53][54] Park et al observed strong photon antibunching as well as blinking behavior ascribed to charge/discharge events triggered by photoionization in CsPbBr 3 and CsPbI 3 . [52] Recently, Becker et al showed the lowest triplet exciton for CsPbX 3 is bright, which explains the anomalously fast emission rates for these materials compared to other semiconductors.…”