Degradation and Self-Healing in Perovskite Solar Cells

Self-healing behavior of superhard covalent bond materials

In recent years, superhard covalently bonded materials have drawn a great deal of attention due to their excellent mechanical properties and potential applications in various fields. This review focuses on the self-healing behavior of these materials, outlining state-of-the-art research results. In detail, we discuss current self-healing mechanisms of self-healing materials including extrinsic healing mechanisms (such as microencapsulation, oxidative healing, shape memory, etc.) and intrinsic healing (dynamic covalent bonding, supramolecular interactions, diffusion, defect-driven processes, etc.). We also provide an overview of the progress in the self-healing behavior of superhard covalently bonded materials and the mechanisms of permanent covalent bonding healing. Additionally, we analyze the factors that influence the healing properties of these materials. Finally, the main findings and an outlook on the future directions and challenges of this emerging field are summarized in the Conclusion section.

Self-healing crystals

Self-healing is an intrinsically exciting concept as it applies to the process of recovery, a commonplace phenomenon found in living organisms. Self-healing of artificial materials is as beneficial to living creatures as it is to materials science, wherein the effect can considerably prolong lifetimes. Although self-healing sodium chloride crystals were discovered in the 1980s, the field entered a renaissance when healing was observed in the emerging materials class of molecular crystals in 2016. Self-healing properties in polymers, cementitious materials, and coatings have already found commercial applications. The reinvigorated interest in self-healing molecular crystals stems from their prospects as durable, lightweight and flexible emissive or electronic materials. Ideally being defectless and ordered media, organic crystals have unique optical, mechanical and electrical properties, and the possibility of self-healing substantially increases their viability for smart devices.

Impact of Hexagonal Boron Nitride Encapsulation on the Photophysical Dynamics of MAPbI3 Perovskite Crystals

Metal halide perovskites are known to suffer from instability due to their high sensitivity to external stimuli. Although encapsulation can considerably improve their stability, the impact of encapsulation on the intrinsic photophysical properties of perovskites remains unclear. Here, we investigate the effect of hexagonal boron nitride (hBN) encapsulation on the photoluminescence (PL) dynamics of MAPbI3 perovskite crystals at the individual crystal level. The results demonstrate that hBN encapsulation leads to PL decline, PL lifetime shortening, and spectral broadening in MAPbI3 crystals, which can be ascribed to the stress exerted by hBN encapsulation on MAPbI3 crystals that promotes defect formation and subsequent nonradiative recombination losses. Furthermore, although hBN encapsulation can delay degradation, the effect of hBN-induced stress and the poor sealing due to single-sided encapsulation would further broaden the spectra over time. This work provides new insights into the photophysical effects of encapsulation on perovskites and has significance for the selection of perovskite encapsulation strategies.

Activated Corrosion and Recovery in Lead Mixed-Halide Perovskites Revealed by Dynamic Near-Ambient Pressure X-ray Photoelectron Spectroscopy

Herein, we quantify rates of O2-photoactivated corrosion and recovery processes within triple cation CsFAMAPb(IBr)3 perovskite active layers using dynamic near-ambient pressure X-ray photoemission spectroscopy (NAP-XPS). Activated corrosion is described as iodide oxidation and lead reduction, which occurs only in the presence of both O2 and light through photoinduced electron transfer. We observe electron density reorganization from the Pb-I bonds consistent with ligand exchange, evident from the nonstoichiometric redox change (i.e., <1 e-). Approximately half of the Pb centers are reduced to weakly coordinated Pb-higher oxidation number than metallic Pb-with a rate coefficient of ∼3 (±0.3) × 10-4 atomic percent/s. Hole capture by I- yields I3- and is accompanied by increased concentrations of near-surface bromides, hypothesized to be due to anion vacancies and/or oxidation of mobile iodide resulting from ion demixing. Activated corrosion is found to be quasi-reversible; initial perovskite stoichiometry slowly recovers when the O2/light catalyst is removed, postulated to be due to mobile halide species present within the film below XPS sampling depth. Small deviations in near-surface composition (<2%) of the perovskite are used to connect reaction rates to quantified, near-band edge donor and acceptor defect concentrations, demonstrating two energetically distinct sites are responsible for the redox process. Collectively, environmental flux and rate quantification are deemed critical for the future elucidation of chemical degradation processes in perovskites, where rate-dependent reaction pathways are expected to be very system dependent (environment and material).

Enhancing the Performance of Hole-Conductor-Free Printable Mesoscopic Perovskite Solar Cells through Polyaniline-Mediated Iodine Recycling and Defect Passivation

Printable mesoscopic perovskite solar cells (p-MPSCs) provide an opportunity for low-cost manufacturing of photovoltaics. However, the performance of p-MPSCs is severely compromised by iodine defects. This study presents a strategy by incorporating polyaniline (PANI) to achieve both iodine recycling and iodine defect passivation to significantly improve the performance of p-MPSCs. PANI captures and immobilizes iodine ions, establishing a stable iodine recycling system that effectively suppresses iodine loss. Additionally, the Lewis base properties of PANI enable it to passivate iodine defects within the perovskite and suppress nonradiative recombination. With the synergistic effects, PANI increases the power conversion efficiency of the champion device from 18.28% to 20.24%. This strategy offers a potential solution for enhancing the performance of p-MPSCs with promising implications for practical applications.

Advances in Self-Healing Perovskite Solar Cells Enabled by Dynamic Polymer Bonds

This comprehensive review addresses the self-healing phenomenon in perovskite solar cells (PSCs), emphasizing the reversible reactions of dynamic bonds as the pivotal mechanism. The crucial role of polymers in both enhancing the inherent properties of perovskite and inducing self-healing phenomena in grain boundaries of perovskite films are exhibited. The review initiates with an exploration of the various stability problems that PSCs encounter, underscoring the imperative to develop PSCs with extended lifespans capable of self-heal following damage from moisture and mechanical stress. Owing to the strong compatibility brought by polymer characteristics, many additive strategies can be employed in self-healing PSCs through artful molecular design. These strategies aim to limit ion migration, prevent moisture ingress, alleviate mechanical stress, and enhance charge carrier transport. By scrutinizing the conditions, efficiency, and types of self-healing behavior, the review encapsulates the principles of dynamic bonds in the polymers of self-healing PSCs. The meticulously designed polymers not only improve the lifespan of PSCs through the action of dynamic bonds but also enhance their environmental stability through functional groups. In addition, an outlook on self-healing PSCs is provided, offering strategic guidance for future research directions in this specialized area.

A ratiometric fluorescent probe based on water-soluble CsPbX3 (Br/I) perovskite nanocrystals for sensitive detection of tetracycline

A dual supersaturation recrystallization method was employed to synthesize water-stable, highly sensitive cesium-lead halide perovskite nanocrystals (CsPbBr3 PNCs). The PNCs exhibited excellent water stability, a significant photoluminescence quantum efficiency of 83.03%, along with a narrow full width at half maximum (FWHM) of 20 nm. Following iodide ion treatment, the fluorescence emission peak of CsPbBr3 PNCs can be tuned from 520 to 681 nm, causing a color transition from green to red. Within the 0-300 μM range, the red shift showed a linear correlation with I- concentration, achieving a detection limit as low as 0.40 μM. It is worth noting that excessive iodide ions could have allowed PNCs to exhibit dual emission with maximum wavelengths of 520 and 681 nm. A ratiometric perovskite nanoprobe was constructed with the green emission peak as an internal standard and the red emission peak as the response signal. The probe demonstrated a strong linear correlation with tetracycline concentrations ranging from 0 to 8 μM, with a detection limit of 88.60 nM (S/N = 3). This research offers valuable insights into the design and development of ratiometric perovskite sensors capable of detecting in aqueous solutions, while also emphasizing the importance of rapidly establishing hydrogen-bonding networks when analyzing such detection systems.

Consistent Interpretation of Time- and Frequency-Domain Traces of Ion Migration in Perovskite Semiconductors

The migration of mobile ions through the metal halide perovskite layer is still one of the main reasons for the poor stability of perovskite solar cells, LEDs, and photodetectors. To characterize mobile ions in the perovskite layer, time- and frequency-based electrical measurements are promising techniques. However, the presence of transport layers complicates their interpretation, limiting the information about mobile ions that can be extracted, and it is not clear how different features in frequency- and time-domain measurements relate to mobile ions. Here, we characterize a transport-layer-free device with capacitance frequency, capacitance transient, and current transient measurements in the dark, under illumination, and at different temperatures. We extract characteristic ionic signatures from the measurements, which we reproduce with drift-diffusion simulations for each technique. This allows us to explain the origins of the different ionic signatures, advancing our understanding of how electronic characterization techniques can be used to study the properties of mobile ions.

Guanidinium Substitution Improves Self-Healing and Photodamage Resilience of MAPbI3

Self-healing materials can become game changers for developing sustainable (opto)electronics. APbX3 halide (=X-) perovskites, HaPs, have shown a remarkable ability to self-heal damage. While we demonstrated self-healing in pure HaP compounds, in single crystals, and in polycrystalline thin films (as used in most devices), HaP compositions with multiple A+ (and X-) constituents are preferred for solar cells. We now show self-healing in mixed A+ HaPs. Specifically, if at least 15 atom % of the methylammonium (MA+) A cation is substituted for by guanidinium (Gua+) or acetamidinium (AA+), then the self-healing rate after damage is enhanced. In contrast, replacing MA+ with dimethylammonium (DMA+), comparable in size to Gua+ or AA+, does not alter this rate. Based on the times for self-healing, we infer that the rate-determining step involves short-range diffusion of A+ and/or Pb2+ cations and that the self-healing rate correlates with the strain in the material, the A+ cation dipole moment, and H-bonding between A+ and I-. These insights may offer clues for developing a detailed self-healing mechanism and understanding the kinetics to guide the design of self-healing materials. Fast recovery kinetics are important from the device perspective, as they allow complete recovery in devices during operation or when switched off (LEDs)/in the dark (photovoltaics).

What Can Chemical Bonding Tell Us about Photoinduced Phase Transition Reactions in Inorganic Semiconductors? Insight from Bismuth-Antimony Selenide

Photoreactive self-healing semiconductors with suitable bandgaps for solar energy conversion offer an intriguing path to making resilient and low-cost photovoltaic devices through the introduction of a self-recovery path. However, only a few inorganic photovoltaic materials have such quality, and the underlying chemical properties that enable it are unknown, which poses a significant limit to our ability to study and discover new self-healing semiconductors. Recently, we have found that antimony trichalcogenide (Sb2Se3 and Sb2S3) and chalcohalides (e.g., SbSeI) can undergo a reversible photoinduced phase transition (PIPT) in which the structure is restored after photoinduced damage incurs to the materials. This group of materials offer a unique opportunity for studying PIPT and its limits. In particular, this group of materials facilitate the study of functional permutation to specific crystalline sites and to finding the limits of PIPT occurrence, which sheds light on the origin of the PIPT and self-recovery of this class of materials. Using Raman spectroscopy of thin films, and following signature vibrations of transition species, we have found that the PIPT magnitude decays upon gradual BiSb(1) substitution in a Sb2-xBixSe3 homologous series, until nearly one in five Sb ions is substituted with Bi. Then, the PIPT diminishes completely. The homologous series occurs along a transition from covalent to metavalent chemical bonding. By expanding our search, we find that a correlation between bonding type and photoreactivity does exist but conclude that it is an insufficient condition. Instead, we suggest, based on bond order and additional DFT calculations, that sufficient bonding states at the bottom of the conduction band are also required. This joint experimental and computational study pushes the limits of designing self-healing inorganic semiconductors for various applications and provides tools for further expansion.

Structural and excitonic properties of the polycrystalline FAPbI3thin films, and their photovoltaic responses

Faormamadinium based perovskites have been proposed to replace the methylammonium lead tri-iodide (MAPbI3) perovskite as the light absorbing layer of photovoltaic cells owing to their photo-active and chemically stable properties. However, the crystal phase transition from the photo-activeα-FAPbI3to the non-perovksiteδ-FAPbI3still occurs in un-doped FAPbI3films owing to the existence of crack defects, which degrads the photovoltaic responses. To investigate the crack ratio (CR)-dependent structure and excitonic characteristics of the polycrystalline FAPbI3thin films deposited on the carboxylic acid functionalized ITO/glass substrates, various spectra and images were measured and analyzed, which can be utilized to make sense of the different devices responses of the resultant perovskite based photovoltaic cells. Our experimental results show that the there is a trade-off between the formations of surface defects and trapped iodide-mediated defects, thereby resulting in an optimal crack density or CR of the un-dopedα-FAPbI3active layer in the range from 4.86% to 9.27%. The decrease in the CR (tensile stress) results in the compressive lattice and thereby trapping the iodides near the PbI6octahedra in the bottom region of the FAPbI3perovskite films. When the CR of the FAPbI3film is 8.47%, the open-circuit voltage (short-circuit current density) of the resultant photovoltaic cells significantly increased from 0.773 V (16.62 mA cm-2) to 0.945 V (18.20 mA cm-2) after 3 d. Our findings help understanding the photovoltaic responses of the FAPbI3perovskite based photovoltaic cells on the different days.

Förster Resonance Energy Transfer and Enhanced Emission in Cs4PbBr6 Nanocrystals Encapsulated in Silicon Nano-Sheets for Perovskite Light Emitting Diode Applications

Encapsulating Cs4PbBr6 quantum dots in silicon nano-sheets not only stabilizes the halide perovskite, but also takes advantage of the nano-sheet for a compatible integration with the traditional silicon semiconductor. Here, we report the preparation of un-passivated Cs4PbBr6 ellipsoidal nanocrystals and pseudo-spherical quantum dots in silicon nano-sheets and their enhanced photoluminescence (PL). For a sample with low concentrations of quantum dots in silicon nano-sheets, the emission from Cs4PbBr6 pseudo-spherical quantum dots is quenched and is dominated with Pb2+ ion/silicene emission, which is very stable during the whole measurement period. For a high concentration of Cs4PbBr6 ellipsoidal nanocrystals in silicon nano-sheets, we have observed Förster resonance energy transfer with up to 87% efficiency through the oscillation of two PL peaks when UV excitation switches between on and off, using recorded video and PL lifetime measurements. In an area of a non-uniform sample containing both ellipsoidal nanocrystals and pseudo-spherical quantum dots, where Pb2+ ion/silicene emissions, broadband emissions from quantum dots, and bandgap edge emissions (515 nm) appear, the 515 nm peak intensity increases five times over 30 min of UV excitation, probably due to a photon recycling effect. This irradiated sample has been stable for one year of ambient storage. Cs4PbBr6 quantum dots encapsulated in silicon nano-sheets can lead to applications of halide perovskite light emitting diodes (PeLEDs) and integration with traditional semiconductor materials.

Regulating Functional Groups to Construct a Mild Passivator Enhancing the Efficiency and Stability of Carbon-Based Perovskite Solar Cells

The abundant defects on the perovskite surface greatly impact the efficiency improvement and long-term stability of carbon-based perovskite solar cells. Molecules with electron-donating or electron-withdrawing functional groups have been cited for passivating various defects. However, few studies have investigated the potential adverse effects arising from the synergistic interactions among functional groups. Herein, we investigate the correlation between functional group configurations and passivation strength as well as the potential adverse impacts of strong electrostatic structures by methodically designing three distinct interface molecules functionalized with different ending groups, which both belong to biguanide derivatives, including 1-(3,4-dichlorophenyl) biguanide hydrochloride (DBGCl), metformin hydrochloride (MFCl), and biguanide hydrochloride (BGCl). The results indicate that DBGCl establishes comparatively mild active sites, not only passivates defects but also aids in forming a surface with a uniform potential. Conversely, MFCl exerts a more pronounced adverse effect on the perovskite surface, which is attributable to the electronic state perturbations induced by its functional groups. Due to the lack of hydrophobic groups, devices treated with BGCl demonstrate insufficient moisture resistance. Devices passivated with DBGCl demonstrate superior average efficiency, showcasing a 12% enhancement relative to the pristine. Furthermore, DBGCl-treated devices exhibit enhanced stability in three different environments, respectively, achieving the highest PCE retention rates under nitrogen conditions (25 °C), room-temperature air conditions (25 °C, RH = 40 ± 2%), and high-temperature air conditions (65 °C, RH = 40 ± 2%).

Unraveling the Degradation Mechanisms of Perovskite Solar Cells under Mechanical Tensile Loads

The short longevity of perovskite solar cells (PSCs) is the major hurdle toward their commercialization. In recent years, mechanical stability has emerged as a pivotal aspect in enhancing the overall durability of PSCs, prompting a myriad of strategies devoted to this issue. However, the mechanical degradation mechanisms of PSCs remain largely unexplored, with corresponding studies mainly limited to perovskite single crystals, neglecting the complexity and nuances present in PSC devices based on polycrystalline perovskite thin films. Herein, we reveal the underlying mechanisms of the mechanical degradation of formamidinium-based PSCs, which are the most prevalent high-performance PSC candidates. Under uniaxial tensile loads, we found that the degradation is mainly attributed to the sequential increase in the density of micropores and halide defects within the perovskite films. This phenomenon is consistent across various perovskite compositions and environmental conditions. Our findings elucidate mechanistic insights for more targeted mitigation strategies aimed at addressing the mechanical degradation of PSC devices.

Unraveling the Heat- and UV-Induced Degradation of Mixed Halide Perovskite Thin Films via Surface Analysis Techniques

In recent years, organic-inorganic hybrid perovskite materials have become one of the most promising materials in the new generation of solar cells. These perovskites can provide excellent photoelectric properties after a simple fabrication process. Although perovskite solar cells have achieved high power conversion efficiency, instability concerns regarding material exposure to heat, moisture, air, and UV light present hindrances to commercialization. In this study, three kinds of perovskites (MAPbI3, MAPbI3-xBrx, and MAPbI3-xClx) were used to investigate the crystal stability upon exposure to heat and UV light. SEM, XRD, and FTIR were used to observe the surface morphology, crystal structure, and functional groups of the perovskite thin films. XPS was used to examine the surface composition and chemical state of the perovskite thin films under different conditions. Among these three types of perovskites, it was found that the MAPbI3-xBrx crystal demonstrated the best stability. ToF-SIMS was used to confirm the molecular distribution of the MAPbI3-xBrx films upon exposure to heat and UV light at different depths. ToF-SIMS revealed that [Pb]+ and [PbI]+ aggregated at the interface between the perovskite and ITO substrate after 14 days of thermal treatment. On the other hand, [Pb]+ and [PbI]+ were distributed uniformly after 3 days of UV exposure. This study systematically analyzed and revealed the thermal- and UV-induced degradation process of three perovskite films by using surface analysis techniques. It was concluded that bromine-doped perovskite films had better stability, and UV light caused more severe damage than heat.

Exploring Non-Toxic Lower Dimensional Perovskites for Next-Generation X-Ray Detectors

Owing to their extraordinary photophysical properties, organometal halide perovskites are emerging as a new material class for X-ray detection. However, the existence of toxic lead makes their commercialization questionable and should readily be replaced. Accordingly, several lead alternatives have been introduced into the framework of conventional perovskites, resulting in various new perovskite dimensionalities. Among these, Pb-free lower dimensional perovskites (LPVKs) not only show promising X-ray detecting properties due to their higher ionic migration energy, wider and tunable energy bandgap, smaller dark currents, and structural versatility but also exhibit extended environmental stability. Herein, first, the structural organization of the PVKs (including LPVKs) is summarized. In the context of X-ray detectors (XDs), the outstanding properties of the LPVKs and active layer synthesis routes are elaborated afterward. Subsequently, their applications in direct XDs are extensively discussed and the device performance, in terms of the synthesis method, device architecture, active layer size, figure of merits, and device stability are tabulated. Finally, the review is concluded with an in-depth outlook, thoroughly exploring the present challenges to LPVKs XDs, proposing innovative solutions, and future directions. This review provides valuable insights into optimizing non-toxic Pb-free perovskite XDs, paving the way for future advancements in the field.

Mechanical Durability and Flexibility in Perovskite Photovoltaics: Advancements and Applications

The remarkable progress in perovskite solar cell (PSC) technology has witnessed a remarkable leap in efficiency within the past decade. As this technology continues to mature, flexible PSCs (F-PSCs) are emerging as pivotal components for a wide array of applications, spanning from powering portable electronics and wearable devices to integrating seamlessly into electronic textiles and large-scale industrial roofing. F-PSCs characterized by their lightweight, mechanical flexibility, and adaptability for cost-effective roll-to-roll manufacturing, hold immense commercial potential. However, the persistent concerns regarding the overall stability and mechanical robustness of these devices loom large. This comprehensive review delves into recent strides made in enhancing the mechanical stability of F-PSCs. It covers a spectrum of crucial aspects, encompassing perovskite material optimization, precise crystal grain regulation, film quality enhancement, strategic interface engineering, innovational developed flexible transparent electrodes, judicious substrate selection, and the integration of various functional layers. By collating and analyzing these dedicated research endeavors, this review illuminates the current landscape of progress in addressing the challenges surrounding mechanical stability. Furthermore, it provides valuable insights into the persistent obstacles and bottlenecks that demand attention and innovative solutions in the field of F-PSCs.

Experimental evidence for defect tolerance in Pb-halide perovskites

The term defect tolerance (DT) is used often to rationalize the exceptional optoelectronic properties of halide perovskites (HaPs) and their devices. Even though DT lacked direct experimental evidence, it became a "fact" in the field. DT in semiconductors implies that structural defects do not translate to electrical and optical effects (e.g., due to charge trapping), associated with such defects. We present pioneering direct experimental evidence for DT in Pb-HaPs by comparing the structural quality of 2-dimensional (2D), 2D-3D, and 3D Pb-iodide HaP crystals with their optoelectronic characteristics using high-sensitivity methods. Importantly, we get information from the materials' bulk because we sample at least a few hundred nanometers, up to several micrometers, from the sample's surface, which allows for assessing intrinsic bulk (and not only surface-) properties of HaPs. The results point to DT in 3D, 2D-3D, and 2D Pb-HaPs. Overall, our data provide an experimental basis to rationalize DT in Pb-HaPs. These experiments and findings will help the search for and design of materials with real DT.

The dynamic surface evolution of halide perovskites induced by external energy stimulation

Tracking the dynamic surface evolution of metal halide perovskite is crucial for understanding the corresponding fundamental principles of photoelectric properties and intrinsic instability. However, due to the volatility elements and soft lattice nature of perovskites, several important dynamic behaviors remain unclear. Here, an ultra-high vacuum (UHV) interconnection system integrated by surface-sensitive probing techniques has been developed to investigate the freshly cleaved surface of CH3NH3PbBr3  in situ under given energy stimulation. On this basis, the detailed three-step chemical decomposition pathway of perovskites has been clarified. Meanwhile, the evolution of crystal structure from cubic phase to tetragonal phase on the perovskite surface has been revealed under energy stimulation. Accompanied by chemical composition and crystal structure evolution, electronic structure changes including energy level position, hole effective mass, and Rashba splitting have also been accurately determined. These findings provide a clear perspective on the physical origin of optoelectronic properties and the decomposition mechanism of perovskites.

Self-Healing Behavior of the Metal Halide Perovskites and Photovoltaics

Perovskite solar cells have achieved rapid progress in the new-generation photovoltaic field, but the commercialization lags behind owing to the device stability issue under operational conditions. Ultimately, the instability issue is attributed to the soft lattice of ionic perovskite crystal. In brief, metal halide perovskite materials are susceptible to structural instability processes, including phase segregation, component loss, lattice distortion, and fatigue failure under harsh external stimuli such as high humidity, strong irradiation, wide thermal cycles, and large stress. Developing self-healing perovskites to further improve the unsatisfactory operational stability of their photoelectric devices under harsh stimuli has become a cutting-edge hotspot in this field. This self-healing behavior needs to be studied more comprehensively. Therefore, the self-healing behavior of the metal halide perovskites and photovoltaics is classified and summarized in this review. By discussing recent advances, underlying mechanisms, strategies, and existing challenges, this review provides perspectives on self-healing of perovskite solar cells in the future.

Degradation and Self-Healing of FAPbBr3 Perovskite under Soft-X-Ray Irradiation

The extensive use of perovskites as light absorbers calls for a deeper understanding of the interaction of these materials with light. Here, the evolution of the chemical and optoelectronic properties of formamidinium lead tri-bromide (FAPbBr3 ) films is tracked under the soft X-ray beam of a high-brilliance synchrotron source by photoemission spectroscopy and micro-photoluminescence. Two contrasting processes are at play during the irradiation. The degradation of the material manifests with the formation of Pb0 metallic clusters, loss of gaseous Br2 , decrease and shift of the photoluminescence emission. The recovery of the photoluminescence signal for prolonged beam exposure times is ascribed to self-healing of FAPbBr3 , thanks to the re-oxidation of Pb0 and migration of FA+ and Br- ions. This scenario is validated on FAPbBr3 films treated by Ar+ ion sputtering. The degradation/self-healing effect, which is previously reported for irradiation up to the ultraviolet regime, has the potential of extending the lifetime of X-ray detectors based on perovskites.

Enhanced Photoluminescence and Prolonged Carrier Lifetime through Laser Radiation Hardening and Self-Healing in Aged MAPbBr3 Perovskites Encapsulated in NiO Nanotubes

Organic-inorganic perovskites hold great promise as optoelectronic semiconductors for pure color light emitting and photovoltaic devices. However, challenges persist regarding their photostability and chemical stability, which limit their extensive applications. This paper investigates the laser radiation hardening and self-healing-induced properties of aged MAPbBr3 perovskites encapsulated in NiO nanotubes (MAPbBr3@NiO) using photoluminescence (PL) and fluorescence lifetime imaging (FLIM). After deliberately subjecting the MAPbBr3@ NiO to atmospheric conditions for two years, the sample remains remarkably stable. It exhibits no changes in PL wavelength during UV laser irradiation and self-healing. Furthermore, exposure to UV light at 375 nm enhances the PL of the self-healed MAPbBr3@NiO. FLIM analysis sheds light on the mechanism behind photodegradation, self-healing, and PL enhancement. The results indicate the involvement of many carrier-trapping states with low lifetime events and an increase in peak lifetime after self-healing. The formation of trapping states at the perovskite/nanotube interface is discussed and tested. This study provides new insights into the dynamics of photo-carriers during photodegradation and self-healing in organic-inorganic perovskites.

A-Site Cation Dependence of Self-Healing in Polycrystalline APbI3 Perovskite Films

In terms of sustainable use, halide perovskite (HaP) semiconductors have a strong advantage over most other classes of materials for (opto)electronics, as they can self-heal (SH) from photodamage. While there is considerable literature on SH in devices, where it may not be clear exactly where damage and SH occur, there is much less on the HaP material itself. Here we perform "fluorescence recovery after photobleaching" (FRAP) measurements to study SH on polycrystalline thin films for which encapsulation is critical to achieving complete and fast self-healing. We compare SH in three photoactive APbI₃ perovskite films by varying the A-site cation ranging from (relatively) small inorganic Cs through medium-sized MA to large FA (the last two are organic cations). While the A cation is often considered electronically relatively inactive, it significantly affects both SH kinetics and the threshold for photodamage. The SH kinetics are markedly faster for γ-CsPbI₃ and α-FAPbI₃ than for MAPbI₃. Furthermore, γ-CsPbI₃ exhibits an intricate interplay between photoinduced darkening and brightening. We suggest possible explanations for the observed differences in SH behavior. This study's results are essential for identifying absorber materials that can regain intrinsic, insolation-induced photodamage-linked efficiency loss during its rest cycles, thus enabling applications such as autonomously sustainable electronics.

Synergistic Effect of Cation Composition Engineering of Hybrid Cs1-x FAx PbBr3 Nanocrystals for Self-Healing Electronics Application

Mixed-cation hybrid perovskite nanocrystal (HPNC) with high crystallinity, color purity, and tunable optical bandgap offers a practical pathway toward next-generation displays. Herein, a two-step modified hot-injection combined with cation compositional engineering and surface treatment to synthesize high-purity cesium/formamidinium lead bromide HPNCs(Cs_1-x FA_x PbBr₃ ) is presented. The optimized Cs_0.5 FA_0.5 PbBr₃ light-emitting devices (LEDs) exhibit uniform luminescence of 3500 cd m^-2 and a prominent current efficiency of 21.5 cd A^-1 . As a proof of concept, a self-healing polymer (SHP) integrated with white LED backlight and laser prototypes exhibited 4 h autonomous self-healing through the synergistic effect of weak reversible imine bonds and stronger H-bonds. First, the SHP-HPNCs-initial and SHP-HPNCs-cut possess high long-term stability and dramatically suppressed lead leakage as low as 0.6 ppm along with a low leakage rate of 1.11 × 10^-5 cm² and 3.36 × 10^-5 cm² even over 6 months in water. Second, the Cs_0.5 FA_0.5 PbBr₃ HPNCs and SHP-induced shattered-repaired perovskite glass substrate show the lowest lasing threshold values of 1.24 and 8.58 µJ cm^-2 , respectively. This work provides an integrative and in-depth approach to exploiting SHP with intrinsic and entropic self-healing capabilities combined with HPNCs to develop robust and reliable soft-electronic backlight and laser applications.