Intrinsically, detrimental defects accumulating at the surface and grain boundaries limit both the performance and stability of perovskite solar cells. Small molecules and bulkier polymers with ...functional groups are utilized to passivate these ionic defects but usually suffer from volatility and precipitation issues, respectively. Here, starting from the addition of small monomers in the PbI2 precursor, a polymerization‐assisted grain growth strategy is introduced in the sequential deposition method. With a polymerization process triggered during the PbI2 film annealing, the bulkier polymers formed will be adhered to the grain boundaries, retaining the previously established interactions with PbI2. After perovskite formation, the polymers anchored on the boundaries can effectively passivate undercoordinated lead ions and reduce the defect density. As a result, a champion power conversion efficiency (PCE) of 23.0% is obtained, together with a prolonged lifetime where 85.7% and 91.8% of the initial PCE remain after 504 h continuous illumination and 2208 h shelf storage, respectively.
A polymerization‐assisted grain growth strategy in the sequential deposition method of perovskite thin films is demonstrated by triggering a polymerization process during PbI2 film annealing. This strategy effectively passivates undercoordinated lead ions, reduces defect density, and boosts power conversion efficiency up to 23.0%, together with a prolonged lifetime.
Manipulation of grain boundaries in polycrystalline perovskite is an essential consideration for both the optoelectronic properties and environmental stability of solar cells as the ...solution-processing of perovskite films inevitably introduces many defects at grain boundaries. Though small molecule-based additives have proven to be effective defect passivating agents, their high volatility and diffusivity cannot render perovskite films robust enough against harsh environments. Here we suggest design rules for effective molecules by considering their molecular structure. From these, we introduce a strategy to form macromolecular intermediate phases using long chain polymers, which leads to the formation of a polymer-perovskite composite cross-linker. The cross-linker functions to bridge the perovskite grains, minimizing grain-to-grain electrical decoupling and yielding excellent environmental stability against moisture, light, and heat, which has not been attainable with small molecule defect passivating agents. Consequently, all photovoltaic parameters are significantly enhanced in the solar cells and the devices also show excellent stability.
The operational instability of perovskite solar cells (PSCs) is known to mainly originate from the migration of ionic species (or charged defects) under a potential gradient. Compositional ...engineering of the “A” site cation of the ABX3 perovskite structure has been shown to be an effective route to improve the stability of PSCs. Here, the effect of size‐mismatch‐induced lattice distortions on the ion migration energetics and operational stability of PSCs is investigated. It is observed that the size mismatch of the mixed “A” site composition films and devices leads to a steric effect to impede the migration pathways of ions to increase the activation energy of ion migration, which is demonstrated through multiple theoretical and experimental evidence. Consequently, the mixed composition devices exhibit significantly improved thermal stability under continuous heating at 85 °C and operational stability under continuous 1 sun illumination, with an extrapolated lifetime of 2011 h, compared to the 222 h of the reference device.
A steric engineering strategy to impede ion migration in perovskite thin films is demonstrated where ion migration is effectively hindered by localized lattice distortions induced by incorporation of oversized A site cations. The steric engineering approach improves the operational lifetime of perovskite solar cells by more than nine‐fold from 222 h to 2011 h.
Compositional engineering has been used to overcome difficulties in fabricating high-quality phase-pure formamidinium perovskite films together with its ambient instability. However, this comes ...alongside an undesirable increase in bandgap that sacrifices the device photocurrent. Here we report the fabrication of phase-pure formamidinium-lead tri-iodide perovskite films with excellent optoelectronic quality and stability. Incorporation of 1.67 mol% of 2D phenylethylammonium lead iodide into the precursor solution enables the formation of phase-pure formamidinium perovskite with an order of magnitude enhanced photoluminescence lifetime. The 2D perovskite spontaneously forms at grain boundaries to protect the formamidinium perovskite from moisture and suppress ion migration. A stabilized power conversion efficiency (PCE) of 20.64% (certified stabilized PCE of 19.77%) is achieved with a short-circuit current density exceeding 24 mA cm
and an open-circuit voltage of 1.130 V, corresponding to a loss-in-potential of 0.35 V, and significantly enhanced operational stability.
Conventional epitaxy of semiconductor films requires a compatible single crystalline substrate and precisely controlled growth conditions, which limit the price competitiveness and versatility of the ...process. We demonstrate substrate-tolerant nano-heteroepitaxy (NHE) of high-quality formamidinium-lead-tri-iodide (FAPbI
) perovskite films. The layered perovskite templates the solid-state phase conversion of FAPbI
from its hexagonal non-perovskite phase to the cubic perovskite polymorph, where the growth kinetics are controlled by a synergistic effect between strain and entropy. The slow heteroepitaxial crystal growth enlarged the perovskite crystals by 10-fold with a reduced defect density and strong preferred orientation. This NHE is readily applicable to various substrates used for devices. The proof-of-concept solar cell and light-emitting diode devices based on the NHE-FAPbI
showed efficiencies and stabilities superior to those of devices fabricated without NHE.
Although metal halide perovskite (MHP) light‐emitting diodes (LEDs) have demonstrated great potential in terms of electroluminescence efficiency, the operational stability of MHP LEDs currently ...remains the biggest bottleneck toward their practical usage. Well‐confined excitons/charge carriers in a dielectric/quantum well based on conventional spatial or potential confinement approaches substantially enhance radiative recombination in MHPs, but an increased surface‐to‐volume ratio and multiphase interfaces likely result in a high degree of surface or interface defect states, which brings about a critical environmentally/operationally vulnerable point on LED stability. Here, an effective solution is suggested to mitigate such drawbacks using strategically designed surface‐2D/bulk‐3D heterophased MHP nanograins for long‐term‐stable LEDs. The 2D surface‐functionalized MHP renders significantly reduced trap density, environmental stability, and an ion‐migration‐immune surface in addition to a fast radiative recombination owing to its spatially and potentially confined charge carriers, simultaneously. As a result, heterophased MHP LEDs show substantial improvement in operational lifetime (T50: >200 h) compared to conventional pure 3D or quasi‐2D counterparts (T50: < 0.2 h) as well as electroluminescence efficiency (surface‐2D/bulk‐3D: ≈7.70 ph per el% and pure 3D: ≈0.46 ph per el%).
An effective solution is suggested to mitigate the drawbacks of metal halide perovskite (MHP) using strategically designed surface‐2D/bulk‐3D heterophased MHP nanograins for long‐term‐stable light‐emitting diodes. The 2D surface‐functionalized MHP renders significantly reduced trap density, environmental stability, and an ion‐migration‐immune surface in addition to a fast radiative recombination, simultaneously.
The dry process is a promising fabrication method for all‐solid‐state batteries (ASSBs) to eliminate energy‐intense drying and solvent recovery steps and to prevent degradation of solid‐state ...electrolytes (SSEs) in the wet process. While previous studies have utilized the dry process to enable thin SSE films, systematic studies on their fabrication, physical and electrochemical properties, and electrochemical performance are unprecedented. Here, different fabrication parameters are studied to understand polytetrafluoroethylene (PTFE) binder fibrillation and its impact on the physio‐electrochemical properties of SSE films, as well as the cycling stability of ASSBs resulting from such SSEs. A counter‐balancing relation between the physio‐electrochemical properties and cycling stability is observed, which is due to the propagating behavior of PTFE reduction (both chemically and electrochemically) through the fibrillation network, resulting in cell failure from current leakage and ion blockage. By controlling PTFE fibrillation, a bilayer configuration of SSE film to enable physio‐electrochemically durable SSE film for both good cycling stability and charge storage capability of ASSBs is demonstrated.
Physical and electrochemical properties as well as cycling stability of dry‐processed solid‐state electrolyte films are systematically evaluated by using polytetrafluoroethylene binder. This study provides insight into binder fibrillation in designing all‐solid‐state architecture to achieve ease of fabrication and stable cycling performance.
Accumulating evidence shows that atrial fibrillation (AF) is associated with an increased risk of dementia. Catheter ablation for AF prolongs the duration of sinus rhythm, thereby improving the ...quality of life. We investigated the association of catheter ablation for AF with the occurrence of dementia.
Using the Korean National Health Insurance Service database, among 194 928 adults with AF treated with ablation or medical therapy (antiarrhythmic or rate control drugs) between 1 January 2005 and 31 December 2015, we studied 9119 patients undergoing ablation and 17 978 patients managed with medical therapy. The time-at-risk was counted from the first medical therapy, and ablation was analysed as a time-varying exposure. Propensity score-matching was used to correct for differences between the groups. During a median follow-up of 52 months, compared with patients with medical therapy, ablated patients showed lower incidence and risk of overall dementia (8.1 and 5.6 per 1000 person-years, respectively; hazard ratio 0.73, 95% confidence interval 0.58-0.93). The associations between ablation and dementia risk were consistently observed after additionally censoring for incident stroke (hazard ratio 0.76, 95% confidence interval 0.61-0.95) and more pronounced in cases of ablation success whereas no significant differences observed in cases of ablation failure. Ablation was associated with lower risks of dementia subtypes including Alzheimer's disease and vascular dementia.
In this nationwide cohort of AF patients treated with catheter ablation or medical therapy, ablation was associated with decreased dementia risk. This relationship was evident after censoring for stroke and adjusting for clinical confounders.
Unstable nature against moisture is one of the major issues of metallic halide perovskite solar cell application. Thin-film encapsulation is known as a powerful approach to notably enhance the ...operational stability of perovskite solar cells in humid environment. However, encapsulation layers with ideal gas barrier performance always require harsh fabrication conditions with high temperature and harmful precursors. For this reason, here we provide a mild encapsulation strategy to maintain the original performance of solar cell devices by utilization of ethylene glycol-induced immediate layer to minimize the damage of plasma-enhanced atomic layer deposition to perovskite solar cells. The organic-inorganic alternating encapsulation structure has exhibited a water vapor transmittance rate of 1.3 × 10−5 g m−2·day−1, which is the lowest value among the reported thin film encapsulation layers of perovskite solar cells. Our perovskite solar cells have survived at 80% relative humidity and 30 °C for over 2000 h while preserving 96% of its initial performance.
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•Plasma enhanced atomic layer deposition was applied to the encapsulation of perovskite solar cells.•Methyl-rich alucone is used to avoid plasma damage to perovskite batteries.•The lowest water vapor transmission rate in the thin film encapsulation of the perovskite solar cells was obtained.•The encapsulated standard MAPbI3 perovskite solar cells maintained 96% of initial efficiency for over 2000 h.•The encapsulated devices maintained 95% the initial performance after 300 mins under water.
Background: Catheter ablation is a good treatment option for atrial fibrillation (AF) in young symptomatic patients. However, there is little information on the efficacy of catheter ablation of ...early-onset AF between sexes. Methods and Results: This study included 1,060 patients under the age 60 years old (837 men, 49.8±7.7 years old, 70.8% paroxysmal AF) who underwent catheter ablation for AF. Sex differences in clinical presentation and ablation outcomes were compared with and without propensity score-matching. During 24.5±18.9 months of follow-up, women showed significantly higher clinical recurrence of AF than men (log-rank, P=0.002). Female sex was independently associated with post-ablation clinical recurrence of AF (adjusted hazard ratio (HR) 2.58 1.06–6.30, P=0.037). Women had a higher proportion of left ventricular diastolic dysfunction (E/Em, P<0.001), higher prevalence of heart failure (P=0.017), greater left atrial (LA) volume index (P=0.001), lower LA endocardial voltage (P<0.001), and higher parasympathetic nervous activity (root-mean square of differences, P<0.001; high-frequency (HF), P=0.010) than men. After a second ablation procedure (n=111), women still showed a higher clinical recurrence rate than men (log-rank, P=0.003) during 22.9±15.0 months of follow-up. Conclusions: Among patients with early-onset AF who underwent catheter ablation, women showed poorer clinical outcomes than men after de novo and second procedures. Left ventricular dysfunction, LA remodeling, and autonomic nervous function may be potential mechanisms underlying sex differences in catheter ablation outcomes of early-onset AF.
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