Nanoscale Visualization of Photodegradation Dynamics of MAPbI₃ Perovskite Films

Abstract

Herein, we report the nanoscale visualization of the photochemical degradation dynamics of MAPbI3 (MA = CH3NH3 +) using infrared scattering scanning near-field microscopy (IR s-SNOM) combined with a series of complementary analytical techniques such as UV–vis and FTIR-spectroscopy, XRD, and XPS. Light exposure of the MAPbI3 films resulted in a gradual loss of MA+ cations starting from the grain boundaries at the film surface and slowly progressing toward the center of the grains and deeper into the bulk perovskite phase. The binary lead iodide PbI2 was found to be the major perovskite photochemical degradation product under the experimental conditions used. Interestingly, the formation of the PbI2 skin over the perovskite grains resulted in a largely enhanced photoluminescence, which resembles the effects observed for core–shell quantum dots. The obtained results demonstrate that IR s-SNOM represents a powerful technique for studying the spatially resolved degradation dynamics of perovskite absorbers and revealing the associated material aging pathways.

Exploring the Limits: Degradation Behavior of Lead Halide Perovskite Films under Exposure to Ultrahigh Doses of γ Rays of Up to 10 MGy

“…It is notable that all four perovskites show a substantial increase in PL intensity after exposure to the highest doses of γ rays (5–10 MGy), which resembles the light-induced degradation of perovskite films studied recently . We believe that the PL enhancement is associated with the phase segregation of the aging products from the pristine perovskite phase.…”

“…All perovskite films revealed complex PL dynamics upon exposure to γ rays (Figure B,C). Both MAPbI 3 and FAPbI 3 show steady increases in PL intensity upon exposure to relatively low doses of γ rays of <100 kGy, which could be explained by the radiation-induced material recrystallization similar to what was observed under visible light illumination. , Indeed, such recrystallization should result in a decrease in the density of defects leading to the nonradiative recombination of charge carriers. On the contrary, the PL intensity of mixed-cation (CsFA)­PbI 3 and (CsMAFA)­PbI 3 perovskite films decayed rapidly upon exposure to even the smallest doses of γ rays (10–50 kGy).…”

“…We have shown recently that infrared scattering-type scanning near-field optical microscopy (IR s-SNOM) is a powerful technique for studying the light-induced degradation of perovskite films with a nanoscale spatial resolution . Herein, we applied this technique to monitor the radiation-induced degradation of perovskite films deposited on plastic (PET) substrates.…”

Oxidative polymerization of triarylamines: a promising route to low-cost hole transport materials for efficient perovskite solar cells

“…The images were collected using IR s-SNOM in pseudoheterodyne (PsHet) mode using a NeaSpec neaSNOM instrument as described previously. 21,22 The measurements were performed at the vibration frequencies of HTMs (PTAA: 1319, P1: 1266, P2 and P3: 1268 cm À1 ), which do not overlap with the IR frequencies of the MA + cation in perovskite (962 and 1249 cm À1 , Fig. S13, ESI †).…”

Thermal and Photo‐Degradation Study of α‐FAPbI3‐Based Perovskite Using In Situ X‐Ray Diffraction

“…A first comprehensive level stems from ex situ and/or post-mortem analysis that allow comparative observations between two different ageing points; being morphological, optical or structural. [13,[39][40] In complementary to this approach, in situ or operando techniques contribute to directly look into the degradation pathways without external manipulation of the material for analysis, or, start and stop in the ageing which may bring unwished effect given the potential perovskite selfhealing properties. [41,42] With this regard, different studies were carried out either on MAPbI 3 or on mixed-cation perovskites using operando transmission electron microscopy (TEM), in situ X-ray diffraction (XRD) or by absorption spectroscopy under different stressors.…”