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1.
J Neuroinflammation ; 17(1): 154, 2020 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-32393298

RESUMO

BACKGROUND: Neuroinflammation plays a vital role in the development and maintenance of neuropathic pain. Recent evidence has proved that bone marrow mesenchymal stem cells (BMSCs) can inhibit neuropathic pain and possess potent immunomodulatory and immunosuppressive properties via secreting a variety of bioactive molecules, such as TNF-α-stimulated gene 6 protein (TSG-6). However, it is unknown whether BMSCs exert their analgesic effect against neuropathic pain by secreting TSG-6. Therefore, the present study aimed to evaluate the analgesic effects of TSG-6 released from BMSCs on neuropathic pain induced by chronic constriction injury (CCI) in rats and explored the possible underlying mechanisms in vitro and in vivo. METHODS: BMSCs were isolated from rat bone marrow and characterized by flow cytometry and functional differentiation. One day after CCI surgery, about 5 × 106 BMSCs were intrathecally injected into spinal cerebrospinal fluid. Behavioral tests, including mechanical allodynia, thermal hyperalgesia, and motor function, were carried out at 1, 3, 5, 7, 14 days after CCI surgery. Spinal cords were processed for immunohistochemical analysis of the microglial marker Iba-1. The mRNA and protein levels of pro-inflammatory cytokines (IL-1ß, TNFα, IL-6) were detected by real-time RT-PCR and ELISA. The activation of the TLR2/MyD88/NF-κB signaling pathway was evaluated by Western blot and immunofluorescence staining. The analgesic effect of exogenous recombinant TSG-6 on CCI-induced mechanical allodynia and heat hyperalgesia was observed by behavioral tests. In the in vitro experiments, primary cultured microglia were stimulated with the TLR2 agonist Pam3CSK4, and then co-cultured with BMSCs or recombinant TSG-6. The protein expression of TLR2, MyD88, p-p65 was evaluated by Western blot. The mRNA and protein levels of IL-1ß, TNFα, IL-6 were detected by real-time RT-PCR and ELISA. BMSCs were transfected with the TSG-6-specific shRNA and then intrathecally injected into spinal cerebrospinal fluid in vivo or co-cultured with Pam3CSK4-treated primary microglia in vitro to investigate whether TSG-6 participated in the therapeutic effect of BMSCs on CCI-induced neuropathic pain and neuroinflammation. RESULTS: We found that CCI-induced mechanical allodynia and heat hyperalgesia were ameliorated by intrathecal injection of BMSCs. Moreover, intrathecal administration of BMSCs inhibited CCI-induced neuroinflammation in spinal cord tissues. The analgesic effect and anti-inflammatory property of BMSCs were attenuated when TSG-6 expression was silenced. We also found that BMSCs inhibited the activation of the TLR2/MyD88/NF-κB pathway in the ipsilateral spinal cord dorsal horn by secreting TSG-6. Meanwhile, we proved that intrathecal injection of exogenous recombinant TSG-6 effectively attenuated CCI-induced neuropathic pain. Furthermore, in vitro experiments showed that BMSCs and TSG-6 downregulated the TLR2/MyD88/NF-κB signaling and reduced the production of pro-inflammatory cytokines, such as IL-1ß, IL-6, and TNF-α, in primary microglia treated with the specific TLR2 agonist Pam3CSK4. CONCLUSIONS: The present study demonstrated a paracrine mechanism by which intrathecal injection of BMSCs targets the TLR2/MyD88/NF-κB pathway in spinal cord dorsal horn microglia to elicit neuroprotection and sustained neuropathic pain relief via TSG-6 secretion.

2.
Shock ; 2020 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-32433208

RESUMO

Macrophages play a key role in the development of sepsis-induced acute respiratory distress syndrome (ARDS). Recent evidence has proved that glycolysis plays an important role in regulating macrophage polarization through metabolic reprogramming. Bone marrow mesenchymal stem cells (BMSCs) can alleviate sepsis-induced lung injury and possess potent immunomodulatory and immunosuppressive properties via secreting exosomes. However, it is unknown whether BMSCs-derived exosomes exert their therapeutic effect against sepsis-induced lung injury by inhibiting glycolysis in macrophages. Therefore, the present study aimed to evaluate the anti-inflammatory effects of exosomes released from BMSCs on acute lung injury induced by lipopolysaccharide (LPS) in mice and explored the possible underlying mechanisms in vitro and in vivo. We found that BMSCs inhibited M1 polarization and promoted M2 polarization in MH-S cells (a murine alveolar macrophage cell line) by releasing exosomes. Further experiments showed that exosomes secreted by BMSCs modulated LPS-treated MH-S cells polarization by inhibiting cellular glycolysis. Moreover, our results showed that BMSCs-derived exosomes down-regulated the expression of several essential proteins of glycolysis via inhibition of HIF-1α. Finally, a model of LPS-induced ARDS in mice was established, we found that BMSCs-derived exosomes ameliorated the LPS-induced inflammation and lung pathological damage. Meanwhile, we found that intratracheal delivery of BMSCs-derived exosomes effectively down-regulated LPS-induced glycolysis in mice lung tissue. These findings reveal new mechanisms of BMSCs-derived exosomes in regulating macrophage polarization which may provide novel strategies for the prevention and treatment of LPS-induced ARDS.

3.
Artigo em Inglês | MEDLINE | ID: mdl-32367688

RESUMO

Halide perovskites have received extensive attention in the field of photocatalysis owing to their excellent optoelectronic properties. However, the semiconductor properties of halide perovskite surface and the influences on the photocatalytic performances have not been systematically clarified. Here we employ the conversion of triose (e.g. 1,3-dihydroxyacetone (DHA)) as a model reaction to explore the surface termination of MAPbI 3 . By rational design of the surface termination for MAPbI 3 , we substantially improve the production rate of butyl lactate to 7719 µg/g cat./h under visible light illumination. It reveals that MAI-terminated MAPbI 3 surface governs the photocatalytic performance. Specially, MAI-terminated surface is susceptible to iodide oxidation, which thus promotes the exposure of Pb(II) as active sites for this photocatalysis process. Moreover, MAI-termination induces p-doping effect near the surface for MAPbI 3 , which facilitates the carrier transport and thus photosynthesis. The understanding of the surface termination in MAPbI 3 photocatalyst suggests a new avenue to engineer halide perovskite semiconductor materials for future photocatalysis.

4.
ACS Nano ; 2020 Apr 23.
Artigo em Inglês | MEDLINE | ID: mdl-32293867

RESUMO

Organic-inorganic hybrid halide perovskites (ABX3), especially layered 2D perovskites, have been recognized as promising semiconductors due to their tunable crystal structure and unique optoelectronic properties. A-site cations, as spacers, allow various metal halide assemblies, but the stacking pattern and the influence of their collective behavior on the properties of the resultant materials remain ambiguous. Here, the cation-stacking effects in the 2D perovskite single crystals, with a focus on the electron-phonon interaction, are investigated. We reveal the different photoluminescence from the surface region and the interior of the crystal, which is due to the residual strain induced by A-site cation stacking. We also examine the cation-stacking effects on the electron-phonon interaction, which is further employed to tailor the optoelectronic properties of the resultant 2D crystals. By reducing the microstrain, we reduce the electron-phonon coupling to improve the mobility and their stability against electric field in the corresponding crystals. Our study suggests a way to manipulate the optoelectronic properties in 2D perovskite materials by rational design of cation stacking.

5.
J Phys Chem Lett ; : 3521-3528, 2020 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-32272840

RESUMO

Quasi-2D halide perovskites have emerged as some of the most promising photovoltaic materials owing to their excellent stability, yet the device power conversion efficiency is far from satisfactory. Besides crystal orientation-related carrier transport, defects in absorbers also play a crucial role in device performance, which has received limited attention in the 2D perovskite field. Herein, we systematically profile the defect states in 2D perovskite film by the temperature-dependent admittance spectroscopy (AS), light intensity-dependent VOC, space-charge-limited-circuit (SCLC), and photoluminescence measurements. It is revealed that the quasi-2D perovskite films suffer from severe defects as compared to the 3D counterparts in terms of both trap energy levels and trap densities. Consequently, the level of nonradiative recombination of photogenerated carriers is much greater in the corresponding devices, wherein the monomolecular recombination is dominant. These findings substantially contribute to a deeper understanding of the nature of 2D perovskite materials, which promotes the further development of 2D perovskite solar cells.

6.
Artigo em Inglês | MEDLINE | ID: mdl-31957946

RESUMO

Lead halide perovskites with mixed cations/anions often suffer from phase segregation, which is detrimental to device efficiency and their long-term stability. During perovskite film growth, the gel stage (in between liquid and crystalline) correlates to phase segregation, which has been rarely explored. Herein, cation diffusion kinetics are systematically investigated at the gel stage to develop a diffusion model obeying Fick's second law. Taking 2D layered perovskite as an example, theoretical and experimental results reveal the impact of diffusion coefficient, temperature, and gel duration on the film growth and phase formation. A homogenous 2D perovskite thin film was then fabricated without significant phase segregation. This in-depth understanding of gel stage and relevant cation diffusion kinetics would further guide the design and processing of halide perovskites with mixed composition to meet requirements for optoelectronic applications.

7.
ACS Appl Mater Interfaces ; 12(2): 3127-3133, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31833753

RESUMO

Two-dimensional (2D) lead halide perovskite has recently been recognized as a promising candidate to stabilize perovskite solar cells due to its extraordinary moisture resistance. These 2D perovskite films often consist of multiple phases with layered (n) lead halide (from n = 1, 2, 3 to ≈∞). However, a convincing evidence is still lacking to clarify the phase distribution with respect to different n, thus causes the misleading for device design. Herein, confocal photoluminescence (PL) spectroscopy was applied to probe the inhomogeneity of 2D perovskite films along the vertical direction to construct a clear-phase distribution mapping consequently. It reveals that the 2D perovskite phases (n = 2, 3, 4) locate preferentially near the substrate, while large n phases are predominantly near the top surface. Moreover, we successfully developed a simple method to manipulate the phase distribution in 2D perovskite thin films, which results in a dramatic increase of device efficiency from 4.95 to 11.6%. Our findings thus provide insights to the understanding of 2D perovskite film growth. The utilization of visualized phase distribution data could also guide the further development of 2D perovskite materials for optoelectronic devices.

8.
Shock ; 53(1): 103-113, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31841452

RESUMO

As tissue-resident cells in the lung, alveolar macrophages display remarkable heterogeneity and play a crucial role in the development and control of septic acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Recent evidence suggests that α-ketoglutarate (α-KG) plays an important role in alternative activation of macrophage (M2) through metabolic and epigenetic reprogramming, and thus possesses anti-inflammatory properties. However, the underlying mechanisms of α-KG's effect on alveolar macrophage polarization and the potential effects of α-KG in ALI/ARDS remain unclear. Here, we examined the effects and mechanisms of α-KG on alveolar macrophage polarization, and investigated the possible effects of α-KG on lipopolysaccharide (LPS)-induced ALI/ARDS in a mouse model. We found that α-KG inhibited M1 macrophage polarization and promoted IL-4-induced M2 macrophage polarization in MH-S cells (a murine alveolar macrophage cell line). Further experiments showed that α-KG down-regulated the expression of M1-polarized marker genes and inhibited the activities of mammalian target of rapamycin complex 1 (mTORC1)/p70 ribosomal protein S6 kinase (p70S6K) signaling pathway in M1-polarized MH-S cells. Moreover, our results showed that α-KG promoted IL-4-induced M2 polarization of MH-S cells by augmenting nuclear translocation of peroxisome proliferator-activated receptor γ (PPARγ) and increasing expression of relevant fatty acid metabolic genes. Finally, using an LPS-induced ALI/ARDS mouse model, we found that α-KG ameliorated the LPS-induced inflammation and lung pathological damage, as well as α-KG pretreated mice had better clinical scores compared with the LPS group. These findings reveal new mechanisms of α-KG in regulating macrophage polarization which may provide novel strategies for the prevention and treatment of inflammatory diseases, including sepsis and septic ALI/ARDS.

9.
Nat Commun ; 10(1): 5190, 2019 11 15.
Artigo em Inglês | MEDLINE | ID: mdl-31729389

RESUMO

As one of next-generation semiconductors, hybrid halide perovskites with tailorable optoelectronic properties are promising for photovoltaics, lighting, and displaying. This tunability lies on variable crystal structures, wherein the spatial arrangement of halide octahedra is essential to determine the assembly behavior and materials properties. Herein, we report to manipulate their assembling behavior and crystal dimensionality by locally collective hydrogen bonding effects. Specifically, a unique urea-amide cation is employed to form corrugated 1D crystals by interacting with bromide atoms in lead octahedra via multiple hydrogen bonds. Further tuning the stoichiometry, cations are bonded with water molecules to create a larger spacer that isolates individual lead bromide octahedra. It leads to zero-dimension (0D) single crystals, which exhibit broadband 'warm' white emission with photoluminescence quantum efficiency 5 times higher than 1D counterpart. This work suggests a feasible strategy to modulate the connectivity of octahedra and consequent crystal dimensionality for the enhancement of their optoelectronic properties.

10.
Anesth Analg ; 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31567322

RESUMO

BACKGROUND: Whether intraoperative positive end-expiratory pressure (PEEP) can reduce the risk of postoperative pulmonary complications remains controversial. We performed a systematic review of currently available literature to investigate whether intraoperative PEEP decreases pulmonary complications in anesthetized patients undergoing surgery. METHODS: We searched PubMed, Embase, and the Cochrane Library to identify randomized controlled trials (RCTs) that compared intraoperative PEEP versus zero PEEP (ZEEP) for postoperative pulmonary complications in adults. The prespecified primary outcome was postoperative pulmonary atelectasis. RESULTS: Fourteen RCTs enrolling 1238 patients met the inclusion criteria. Meta-analysis using a random-effects model showed a decrease in postoperative atelectasis (relative risk [RR], 0.51; 95% confidence interval [CI], 0.35-0.76; trial sequential analyses [TSA]-adjusted CI, 0.10-2.55) and postoperative pneumonia (RR, 0.48; 95% CI, 0.27-0.84; TSA-adjusted CI, 0.05-4.86) in patients receiving PEEP ventilation. However, TSA showed that the cumulative Z-curve of 2 outcomes crossed the conventional boundary but did not cross the trial sequential monitoring boundary, indicating a possible false-positive result. We observed no effect of PEEP versus ZEEP ventilation on postoperative mortality (RR, 1.78; 95% CI, 0.55-5.70). CONCLUSIONS: The evidence that intraoperative PEEP reduces postoperative pulmonary complications is suggestive but too unreliable to allow definitive conclusions to be drawn.

11.
Adv Mater ; 31(48): e1904408, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31617644

RESUMO

To improve the photovoltaic performance (both efficiency and stability) in hybrid organic-inorganic halide perovskite solar cells, perovskite lattice distortion is investigated with regards to residual stress (and strain) in the polycrystalline thin films. It is revealed that residual stress is concentrated at the surface of the as-prepared film, and an efficient method is further developed to release this interfacial stress by A site cation alloying. This results in lattice reconstruction at the surface of polycrystalline thin films, which in turn results in low elastic modulus. Thus, a "bone-joint" configuration is constructed within the interface between the absorber and the carrier transport layer, which improves device performance substantially. The resultant photovoltaic devices exhibit an efficiency of 21.48% with good humidity stability and improved resistance against thermal cycling.

12.
Adv Mater ; 31(24): e1900390, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31012204

RESUMO

Crystal orientation has a great impact on the properties of perovskite films and the resultant device performance. Up to now, the exquisite control of crystal orientation (the preferred crystallographic planes and the crystal stacking mode with respect to the particular planes) in mixed-cation perovskites has received limited success, and the underlying mechanism that governs device performance is still not clear. Here, a thermodynamically favored crystal orientation in formamidinium/methylammonium (FA/MA) mixed-cation perovskites is finely tuned by composition engineering. Density functional theory calculations reveal that the FA/MA ratio affects the surface energy of the mixed perovskites, leading to the variation of preferential orientation consequently. The preferable growth along the (001) crystal plane, when lying parallel to the substrates, affects their charge transportation and collection properties. Under the optimized condition, the mixed-cation perovskite (FA1- x MAx PbI2.87 Br0.13 (Cl)) solar cells deliver a champion power conversion efficiency over 21%, with a certified efficiency of 20.50 ± 0.50%. The present work not only provides a vital step in understanding the intrinsic properties of mixed-cation perovskites but also lays the foundation for further investigation and application in perovskite optoelectronics.

13.
Nat Commun ; 10(1): 1112, 2019 03 07.
Artigo em Inglês | MEDLINE | ID: mdl-30846692

RESUMO

Further minimizing the defect state density in the semiconducting absorber is vital to boost the power conversion efficiency of solar cells approaching Shockley-Queisser limit. However, it lacks a general strategy to control the precursor chemistry for defects density reduction in the family of iodine based perovskite. Here the alkaline environment in precursor solution is carefully investigated as an effective parameter to suppress the incident iodine and affects the crystallization kinetics during film fabrication, via rationale adjustment of the alkalinity of additives. Especially, a 'residual free' weak alkaline is proposed not only to shrink the bandgap of the absorber by modulating the stoichiometry of organic cation, but also to improve the open circuit voltage in the resultant device. Consequently, the certified efficiency of 20.87% (Newport) is achieved with one of the smallest voltage deficits of 413 mV in the planar heterojunction perovskite solar cell.

14.
Nat Commun ; 10(1): 815, 2019 02 18.
Artigo em Inglês | MEDLINE | ID: mdl-30778061

RESUMO

The mixed halide perovskites have emerged as outstanding light absorbers for efficient solar cells. Unfortunately, it reveals inhomogeneity in these polycrystalline films due to composition separation, which leads to local lattice mismatches and emergent residual strains consequently. Thus far, the understanding of these residual strains and their effects on photovoltaic device performance is absent. Herein we study the evolution of residual strain over the films by depth-dependent grazing incident X-ray diffraction measurements. We identify the gradient distribution of in-plane strain component perpendicular to the substrate. Moreover, we reveal its impacts on the carrier dynamics over corresponding solar cells, which is stemmed from the strain induced energy bands bending of the perovskite absorber as indicated by first-principles calculations. Eventually, we modulate the status of residual strains in a controllable manner, which leads to enhanced PCEs up to 20.7% (certified) in devices via rational strain engineering.

15.
Small ; 15(6): e1804152, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30645019

RESUMO

The low-dimensional halide perovskites have received enormous attention due to their unique photovoltaic and optoelectronic performances. Periodic spacers are used to inhibit the growth of 3D perovskite and fabricate a 2D counterpart with layered structure, mostly based on organic/inorganic cations. Herein, by introducing organic anions (e.g., pentanedioic acid (PDA) and hexanedioic acid (HDA) simultaneously), leaf-shaped (Cs3 Pb2 Br5 )2 (PDA-HDA) microplates with low-dimensional structure are synthesized. They also exhibit significant photoluminescence (PL) centered at 540 nm with a narrow emission peak. The synthesis of single crystals of Pb(PDA) and Pb(HDA) allows to further clarify the crystal structure of (Cs3 Pb2 Br5 )2 (PDA-HDA) perovskite and its structural evolution mechanism. Moreover, the cooperative introduction of dicarboxylic acid pairs with appropriate lengths is thermodynamically favored for the low-dimensional perovskite crystallization. The temperature-dependent PL indicates a V-shaped Stokes shift with elevated temperature that could be associated with the localization of excitons in the inorganic layers between organic dicarboxylic acid molecules. This work demonstrates low-dimensional halide perovskite with anionic spacers, which also opens up a new approach to the growth of low-dimensional organic-inorganic hybrid perovskite crystals.

16.
Science ; 363(6424): 265-270, 2019 01 18.
Artigo em Inglês | MEDLINE | ID: mdl-30655439

RESUMO

The components with soft nature in the metal halide perovskite absorber usually generate lead (Pb)0 and iodine (I)0 defects during device fabrication and operation. These defects serve as not only recombination centers to deteriorate device efficiency but also degradation initiators to hamper device lifetimes. We show that the europium ion pair Eu3+-Eu2+ acts as the "redox shuttle" that selectively oxidized Pb0 and reduced I0 defects simultaneously in a cyclical transition. The resultant device achieves a power conversion efficiency (PCE) of 21.52% (certified 20.52%) with substantially improved long-term durability. The devices retained 92% and 89% of the peak PCE under 1-sun continuous illumination or heating at 85°C for 1500 hours and 91% of the original stable PCE after maximum power point tracking for 500 hours, respectively.

17.
J Am Chem Soc ; 140(44): 14938-14944, 2018 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-30354087

RESUMO

We report the fused ring electron acceptor (FREA)-perovskite hybrid as a promising platform to fabricate organic-inorganic hybrid solar cells with simple preparation, high efficiency, and good stability. The FREA-perovskite hybrid films exhibit larger grain sizes and stronger crystallinity than the pristine perovskite films. Moreover, the FREA molecules can form coordination bonding with undercoordinated Pb atoms and passivate the trap states in the perovskite films. Time-resolved photoluminescence and transient absorption measurements reveal that FREA facilitates efficient electron extraction and collection. Transient photocurrent and photovoltage measurements suggest faster charge transfer and reduced charge recombination in solar cells based on FREA-perovskite hybrid films. Consequently, solar cells based on FREA-perovskite hybrid films yield a champion efficiency of 21.7% with enhanced stability, which is higher than that of the control devices based on pristine perovskite films (19.6%).

18.
Artigo em Inglês | MEDLINE | ID: mdl-30344613

RESUMO

"Xuebijing Injection" (XBJ) is a traditional Chinese medicine and has been wildly used in the treatment of sepsis in China. However, few studies have reported the use of XBJ in sepsis with acute lung injury (ALI). This study aimed to investigate the therapeutic efficacy of XBJ against sepsis-induced ALI. Generally a total of 27 mice were equally randomized into three groups: a sham group was given saline before sham operation. A sepsis group received the cecal ligation and puncture (CLP) operation only. A sepsis+XBJ group, XBJ, was injected at 72, 48, and 24 h before CLP operation. The lung tissue was collected for UHPLC-Q-TOF/MS profiling analysis, biomarker identification, and pathway analysis. With the analysis of principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA), forty-five purine, amino acid, and sphingolipid metabolites in lung tissues were identified as potential biomarkers of sepsis-induced ALI, among which 22 were reversed in the sepsis+XBJ group significantly. Conclusively, our results suggest that purine metabolic pathway, glutathione metabolic pathway, sphingomyelin metabolic pathway, arachidonic acid metabolic pathway, and phospholipid metabolic pathway may be the potential therapeutic pathways to overcome sepsis-induced acute lung injury and we provided the potential mechanisms of protective effects of XBJ against ALI.

19.
Nat Commun ; 9(1): 2793, 2018 07 18.
Artigo em Inglês | MEDLINE | ID: mdl-30022027

RESUMO

Crystal orientations in multiple orders correlate to the properties of polycrystalline materials, and it is critical to manipulate these microstructural arrangements to enhance device performance. Herein, we report a controllable approach to manipulate the facet orientation within the ABX3 hybrid perovskites polycrystalline films by cation cascade doping at A-site. Two-dimensional synchrotron radiation grazing incidence wide-angle X-ray scattering is employed to probe the crystal orientations in multiple orders in mixed perovskites thin films, revealing a general pattern to guide crystal planes stacking upon extrinsic doping during crystallization. Different from previous studies, this method enables to adjust the crystal stacking mode of certain crystallographic planes in polycrystalline perovskites. Moreover, the preferred facet orientation is found to facilitate photocarrier transport across the absorber and pertaining interface in the resultant PV device, which provides an exemplary paradigm for further explorations that relate to the microstructures of hybrid perovskite materials and relevant optoelectronics.

20.
Adv Mater ; : e1800544, 2018 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-29882254

RESUMO

The power conversion efficiency of organic-inorganic hybrid perovskite solar cells has increased rapidly, but the device stability remains a big challenge. Previous studies show the grain boundary (GB) can facilitate ion migration and initiate device degradation. Herein, methimazole (MMI) is employed for the first time to construct a surface "patch" by in situ converting residual PbI2 at GBs. The resultant MMI-PbI2 complex can effectively suppress ion migration and inhibit diffusion of the metal electrodes. The origin of the surface "patch" effect and their working mechanisms are investigated experimentally and theoretically at the microscopic level. It hence demonstrates a simple and effective method to prolong the device stability in the context of GB engineering, which could be extensively applied to perovskite-based optoelectronics.

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