Electrolyte Design Enables Rechargeable LiFePO4/Graphite Batteries from -80°C to 80°C.

Lithium iron phosphate (LFP)/graphite batteries have long dominated the energy storage battery market and are anticipated to become the dominant technology in the global power battery market. However, the poor fast-charging capability and low-temperature performance of LFP/graphite batteries seriously hinder their further spread. These limitations are strongly associated with the interfacial Li-ion transport. Here we report a wide-temperature-range ester-based electrolyte that exhibits high ionic conductivity, fast interfacial kinetics and excellent film-forming ability by regulating the anion chemistry of Li salt. The interfacial barrier of the battery is quantitatively unraveled by employing three-electrode system and distribution of relaxation time technique. The superior role of the proposed electrolyte in preventing Li0 plating and sustaining homogeneous and stable interphases are also systematically investigated. The LFP/graphite cells exhibit rechargeability in an ultrawide temperature range of -80°C to 80°C and outstanding fast-charging capability without compromising lifespan. Specially, the practical LFP/graphite pouch cells achieve 80.2% capacity retention after 1200 cycles (2 C) and 10-min charge to 89% (5 C) at 25°C and provides reliable power even at -80°C.

Stable Cycling of All-Solid-State Lithium Batteries Enabled by Cyano-Molecular Diamond Improved Polymer Electrolytes.

The interfacial instability of the poly(ethylene oxide) (PEO)-based electrolytes impedes the long-term cycling and further application of all-solid-state lithium metal batteries. In this work, we have shown an effective additive 1-adamantanecarbonitrile, which contributes to the excellent performance of the poly(ethylene oxide)-based electrolytes. Owing to the strong interaction of the 1-Adamantanecarbonitrile to the polymer matrix and anions, the coordination of the Li+-EO is weakened, and the binding effect of anions is strengthened, thereby improving the Li+ conductivity and the electrochemical stability. The diamond building block on the surface of the lithium anode can suppress the growth of lithium dendrites. Importantly, the 1-Adamantanecarbonitrile also regulates the formation of LiF in the solid electrolyte interface and cathode electrolyte interface, which contributes to the interfacial stability (especially at high voltages) and protects the electrodes, enabling all-solid-state batteries to cycle at high voltages for long periods of time. Therefore, the Li/Li symmetric cell undergoes long-term lithium plating/stripping for more than 2000 h. 1-Adamantanecarbonitrile-poly(ethylene oxide)-based LFP/Li and 4.3 V Ni0.8Mn0.1Co0.1O2/Li all-solid-state batteries achieved stable cycles for 1000 times, with capacity retention rates reaching 85% and 80%, respectively.

Revealing the vertical structure of in-situ fabricated perovskite nanocrystals films toward efficient pure red light-emitting diodes.

The development of efficient perovskite light-emitting diodes (PeLEDs) relies strongly on the fabrication of perovskite films with rationally designed structures (grain size, composition, surface, etc.). Therefore, an understanding of structure-performance relationships is of vital importance for developing high-performance perovskite devices, particularly for devices with in-situ fabricated perovskite nanocrystal films. In this study, we reveal the vertical structure of an in-situ fabricated quasi-two-dimensional perovskite film. By combining time-of-flight secondary ion mass spectrometry, energy dispersive spectroscopy, grazing incidence wide-angle X-ray scattering (GIWAXS), and low-temperature photoluminescence spectra, we illustrate that the resulting in-situ fabricated DPPA2Csn-1Pbn(Br0.3I0.7)3n+1 (DPPA+: 3,3-diphenylpropylammonium) film has a gradient structure with a very thin layer of ligands on the surface, predominantly small-n domains at the top, and predominantly large-n domains at the bottom owing to the solubility difference of the precursors. In addition, GIWAXS measurements show that the domain of n = 2 on the top layer has an ordered in-plane alignment. Based on the understanding of the film structure, we developed an in-situ fabrication process with ligand exchange to achieve efficient pure red PeLEDs at 638 nm with an average external quantum efficiency (EQE) of 7.4%. The optimized device had a maximum luminance of 623 cd/m2 with a peak EQE of 9.7%.

Electrochemical biosensor for sensitive detection of SARS-CoV-2 gene fragments using Bi2Se3 topological insulator.

In this study, we have designed an electrochemical biosensor based on topological material Bi2Se3 for the sensitive detection of SARS-CoV-2 in the COVID-19 pandemic. Flake-shaped Bi2Se3 was obtained directly from high-quality single crystals using mechanical exfoliation, and the single-stranded DNA was immobilized onto it. Under optimal conditions, the peak current of the differential pulse voltammetry method exhibited a linear relationship with the logarithm of the concentration of target-complementary-stranded DNA, ranging from 1.0 × 10-15 to 1.0 × 10-11 M, with a detection limit of 3.46 × 10-16 M. The topological material Bi2Se3, with Dirac surface states, enhanced the signal-to-interference plus noise ratio of the electrochemical measurements, thereby improving the sensitivity of the sensor. Furthermore, the electrochemical sensor demonstrated excellent specificity in recognizing RNA. It can detect complementary RNA by amplifying and transcribing the initial DNA template, with an initial DNA template concentration ranging from 1.0 × 10-18 to 1.0 × 10-15 M. Furthermore, the sensor also effectively distinguished negative and positive results by detecting splitting-synthetic SARS-CoV-2 pseudovirus with a concentration of 1 copy/µL input. Our work underscores the immense potential of the electrochemical sensing platform based on the topological material Bi2Se3 in the detection of pathogens during the rapid spread of acute infectious diseases.

Healable and Conductive Two-Dimensional Sulfur Iodide for High-Rate Sodium Batteries.

Self-healing functional materials can repair cracks and damage inside the battery, ensuring the stability of the battery material structure. This feature minimizes performance degradation during the charging and discharging processes, improving the efficiency and stability of the battery. Here, we have developed a novel healing conductive two-dimensional sulfur iodide (SI4) composite cathode. This process integrates both sulfur and iodine compounds into carbon nanocages, forming a SI4@C core-shell structure. This cathode design improves electrical conductivity and repairability, facilitates rapid activation, and ensures structural integrity, resulting in a typical Na-SI4 battery with high capacity and an exceptionally long cycle life. At 10.0 A g-1, the capacity of the Na-SI4 battery can still reach 217.4 mAh g-1 after more than 500 cycles, and the capacity decay rate per cycle is only 0.06%. In addition, the cathode exhibits a cascade redox reaction involving S and I, contributing to its high capacity. The in situ growth of a carbon shell further enhances the conductivity and structural robustness of the entire cathode. The flexibility and bendability of SI4@C-carbon cloth make it applicable for flexible electronic devices, providing more possibilities for battery design. The strategy of engineering a two-dimensional self-healing structure to construct a superior cathode is expected to be widely applied to other electrode materials. This study provides a new pathway for designing novel binary-conversion-type sodium-ion batteries with excellent long-term cycling performance.

Epitaxy of Antimonene Thin Films with Screw Dislocations for the Application of Saturable Absorbers.

The exotic optoelectronic properties of antimonene, including strain-induced tunable bandgaps, broad nonlinear refractive response, etc., have evoked profound upsurges for decades. As the screw dislocations break the crystal symmetry and modify interlayer coupling, it is highly desirable to investigate the optical prospects of antimonene with screw dislocations. Herein, controllable epitaxy of spiral ß-antimonene is achieved on Fe3GaTe2 substrates. By fine-tuning growth temperatures, the evolutions of spiral ß-antimonene with non-centrosymmetric stacking are investigated via scanning tunneling microscopy. The effects of interfacial strain and dislocation motion during screw-dislocation-driven growth are also studied. Additionally, a modulation depth of 40.8% and mode locking at 1558 nm with a pulse width of 290 fs are observed in Er-doped pulsed fiber lasers generated with spiral Sb-based saturable absorbers, revealing superior performance that far outstrips reported Sb-based saturable absorbers to date. Our work sheds light on the preparation of Sb films with screw dislocations and demonstrates a promising approach toward fabricating ultrafast optical devices.

Stabilizing the Bulk-Phase and Solid Electrolyte Interphase of Silicon Microparticle Anode by Constructing Gradient-Hierarchically Ordered Conductive Networks.

The poor bulk-phase and interphase stability, attributable to adverse internal stress, impede the cycling performance of silicon microparticles (µSi) anodes and the commercial application for high-energy-density lithium-ion batteries. In this work, a groundbreaking gradient-hierarchically ordered conductive (GHOC) network structure, ingeniously engineered to enhance the stability of both bulk-phase and the solid electrolyte interphase (SEI) configurations of µSi, is proposed. Within the GHOC network architecture, two-dimensional (2D) transition metal carbides (Ti3C2Tx) act as a conductive "brick", establishing a highly conductive inner layer on µSi, while the porous outer layer, composed of one-dimensional (1D) Tempo-oxidized cellulose nanofibers (TCNF) and polyacrylic acid (PAA) macromolecule, functions akin to structural "rebar" and "concrete", effectively preserves the tightly interconnected conductive framework through multiple bonding mechanisms, including covalent and hydrogen bonds. Additionally, Ti3C2Tx enhances the development of a LiF-enriched SEI. Consequently, the µSi-MTCNF-PAA anode presents a high discharge capacity of 1413.7 mAh g-1 even after 500 cycles at 1.0 C. Moreover, a full cell, integrating LiNi0.8Mn0.1Co0.1O2 with µSi-MTCNF-PAA, exhibits a capacity retention rate of 92.0% following 50 cycles. This GHOC network structure can offer an efficacious pathway for stabilizing both the bulk-phase and interphase structure of anode materials with high volumetric strain.

Spatially selective defect management of CsPbI3 films for high-performance carbon-based inorganic perovskite solar cells.

Defects formed at the surface, buried interface and grain boundaries (GB) of CsPbI3 perovskite films considerably limit photovoltaic performance. Such defects could be passivated effectively by the most prevalent post modification strategy without compromising the photoelectric properties of perovskite films, but it is still a great challenge to make this strategy comprehensive to different defects spatially distributed throughout the films. Herein, a spatially selective defect management (SSDM) strategy is developed to roundly passivate various defects at different locations within the perovskite film by a facile one-step treatment procedure using a piperazine-1,4-diium tetrafluoroborate (PZD(BF4)2) solution. The small-size PZD2+ cations could penetrate into the film interior and even make it all the way to the buried interface of CsPbI3 perovskite films, while the BF4- anions, with largely different properties from I- anions, mainly anchor on the film surface. Consequently, virtually all the defects at the surface, buried interface and grain boundaries of CsPbI3 perovskite films are effectively healed, leading to significantly improved film quality, enhanced phase stability, optimized energy level alignment and promoted carrier transport. With these films, the fabricated CsPbI3 PSCs based on carbon electrode (C-PSCs) achieve an efficiency of 18.27%, which is among the highest-reported values for inorganic C-PSCs, and stability of 500 h at 85 °C with 65% efficiency maintenance.

Bipolar Polymeric Protective Layer for Dendrite-Free and Corrosion-Resistant Lithium Metal Anode in Ethylene Carbonate Electrolyte.

The unstable interface between Li metal and ethylene carbonate (EC)-based electrolytes triggers continuous side reactions and uncontrolled dendrite growth, significantly impacting the lifespan of Li metal batteries (LMBs). Herein, a bipolar polymeric protective layer (BPPL) is developed using cyanoethyl (-CH2CH2C≡N) and hydroxyl (-OH) polar groups, aiming to prevent EC-induced corrosion and facilitating rapid, uniform Li+ ion transport. Hydrogen-bonding interactions between -OH and EC facilitates the Li+ desolvation process and effectively traps free EC molecules, thereby eliminating parasitic reactions. Meanwhile, the -CH2CH2C≡N group anchors TFSI- anions through ion-dipole interactions, enhancing Li+ transport and eliminating concentration polarization, ultimately suppressing the growth of Li dendrite. This BPPL enabling Li|Li cell stable cycling over 750 cycles at 10 mA cm-2 for 2 mAh cm-2. The Li|LiNi0.8Mn0.1Co0.1O2 and Li|LiFePO4 full cells display superior electrochemical performance. The BPPL provides a practical strategy to enhanced stability and performance in LMBs application.

Physically and Chemically Stable Molybdenum-Based Composite Electrodes for p-i-n Perovskite Solar Cells.

Metal halide perovskite solar cells (PSCs) have garnered much attention in recent years. Despite the remarkable advancements in PSCs utilizing traditional metal electrodes, challenges such as stability concerns and elevated costs have necessitated the exploration of innovative electrode designs to facilitate industrial commercialization. Herein, a physically and chemically stable molybdenum (Mo) electrode is developed to fundamentally tackle the instability factors introduced by electrodes. The combined spatially resolved element analyses and theoretical study demonstrate the high diffusion barrier of Mo ions within the device. Structural and morphology characterization also reveals the negligible plastic deformation and halide-metal reaction during aging when Mo is in contact with perovskite (PVSK). The electrode/underlayer junction is further stabilized by a thin seed layer of titanium (Ti) to improve Mo film's uniformity and adhesion. Based on a corresponding p-i-n PSCs (ITO/PTAA/PVSK/C60/SnO2/ITO/Ti/Mo), the champion sample could deliver an efficiency of 22.25%, which is among the highest value for PSCs based on Mo electrodes. Meanwhile, the device shows negligible performance decay after 2000 h operation, and retains 91% of the initial value after 1300 h at 50-60 °C. In summary, the multilayer Mo electrode opens an effective avenue to all-round stable electrode design in high-performance PSCs.

Water-Assisted Growth of Twisted 3R-Stacked MoSe2 Spirals and Its Dramatically Enhanced Second Harmonic Generations.

Enhanced second-harmonic generation (SHG) responses are reported in monolayer transition metal dichalcogenides (e.g., MX2 , M: Mo, W; X: S, Se) due to the broken symmetries. The 3R-like stacked MX2 spiral structures possessing the similar broken inversion symmetry should present dramatically enhanced SHG responses, thus providing great flexibility in designing miniaturized on-chip nonlinear optical devices. To achieve this, the first direct synthesis of twisted 3R-stacked chiral molybdenum diselenide (MoSe2 ) spiral structures with specific screw dislocations (SD) arms is reported, via designing a water-assisted chemical vapor transport (CVT) approach. The study also clarifies the formation mechanism of the MoSe2 spiral structures, by precisely regulating the precursor supply accompanying with multiscale characterizations. Significantly, an up to three orders of magnitude enhancement of the SHG responses in twisted 3R stacked MoSe2 spirals is demonstrated, which is proposed to arise from the synergistic effects of broken inversion symmetry, strong light-matter interaction, and band nesting effects. Briefly, the work provides an efficient synthetic route for achieving the 3R-stacked TMDCs spirals, which can serve as perfect platforms for promoting their applications in on-chip nonlinear optical devices.

Engineering Amorphous-Crystallized Interface of ZrNx Barriers for Stable Inverted Perovskite Solar Cells.

It is challenging to achieve long-term stability of perovskite solar cells due to the corrosion and diffusion of metal electrodes. Integration of compact barriers into devices has been recognized as an effective strategy to protect the perovskite absorber and electrode. However, the difficulty is to construct a thin layer of a few nanometers that can delay ion migration and impede chemical reactions simultaneously, in which the delicate microstructure design of a stable material plays an important role. Herein, ZrNx barrier films with high amorphization are introduced in p-i-n perovskite solar cells. To quantify the amorphous-crystalline (a-c) density, pattern recognition techniques are employed. It is found the decreasing a-c interface in an amorphous film leads to dense atom arrangement and uniform distribution of chemical potential, which retards the interdiffusion at the interface between ions and metal atoms and protect the electrodes from corrosion. The resultant solar cells exhibit improved operational stability, which retains 88% of initial efficiency after continuous maximum power point tracking under 1-Sun illumination at room temperature (25 °C) for 1500 h.

Sensitive biosensors based on topological insulator Bi2Se3 and peptide.

In this work, we designed a facile and label-free electrochemical biosensor based on intrinsic topological insulator (TI) Bi2Se3 and peptide for the detection of immune checkpoint molecules. With topological protection, Bi2Se3 could have robust surface states with low electronic noise, which was beneficial for the stable and sensitive electron transport between electrode and electrolyte interface. The peptides are easily synthesized and chemically modified, and have good biocompatibility and bioavailability, which is a suitable candidate as the recognition units for immune checkpoint molecules. Therefore, the peptide/Bi2Se3 was developed as a suitable working electrode for the electrochemical biosensor. The basic performance of the designed peptide/Bi2Se3 biosensor was investigated to determine the Anti-HA Tag Antibody and PD-L1 molecules. The linear detection range was from 3.6 × 10-10 mg mL-1 to 3.6 × 10-5 mg mL-1, and the detection limit was 1.07 × 10-11 mg mL-1. Moreover, the biosensor also displayed good selectivity and stability.

Topological insulator Bi2Se3 based electrochemical aptasensors for the application of sensitive detection of interferon-γ.

Interferon-γ (IFN-γ) is one of the crucial inflammatory cytokines as an early indicator of multiple diseases. A fast, simple, sensitive and reliable IFN-γ detection method is valuable for early diagnosis and monitoring of treatment. In this work, we creatively developed an electrochemical aptasensor based on the topological material Bi2Se3 for sensitive IFN-γ quantification. The high-quality Bi2Se3 sheet was directly exfoliated from a single crystal, which immobilized the synthesized IFN-γ aptamer. Under optimal conditions, the electrochemical signal revealed a wide linear relation along with the logarithmic concentration of IFN-γ from 1.0 pg mL-1 to 100.0 ng mL-1, with the limit of detection as low as 0.5 pg mL-1. The topological material Bi2Se3 with Dirac surface states improved the electrochemical signal/noise ratio and thus the sensitivity of the sensors. Furthermore, this electrochemical aptasensor exhibited excellent specificity and stability, which could be attributed to the large-scale smooth surface of the Bi2Se3 sheet with few defects decreasing the non-specific absorption. The developed biosensor has the same good performance as the ELISA method for detecting the real serum samples. Our work demonstrates that the developed electrochemical aptasensors based on topological materials have great potential in the field of clinical determination.

Initializing film homogeneity to retard phase segregation for stable perovskite solar cells.

The mixtures of cations and anions used in hybrid halide perovskites for high-performance solar cells often undergo element and phase segregation, which limits device lifetime. We adapted Schelling's model of segregation to study individual cation migration and found that the initial film inhomogeneity accelerates materials degradation. We fabricated perovskite films (FA1-xCsxPbI3; where FA is formamidinium) through the addition of selenophene, which led to homogeneous cation distribution that retarded cation aggregation during materials processing and device operation. The resultant devices achieved enhanced efficiency and retained >91% of their initial efficiency after 3190 hours at the maximum power point under 1 sun illumination. We also observe prolonged operational lifetime in devices with initially homogeneous FACsPb(Br0.13I0.87)3 absorbers.

Reversible Phase Transition for Durable Formamidinium-Dominated Perovskite Photovoltaics.

Phase instability is one of the major obstacles to the wide application of formamidinium (FA)-dominated perovskite solar cells (PSCs). An in-depth investigation on relevant phase transitions is urgently needed to explore more effective phase-stabilization strategies. Herein, the reversible phase-transition process of FA1- x Csx PbI3 perovskite between photoactive phase (α phase) and non-photoactive phase (δ phase) under humidity, as well as the reversible healing of degraded devices, is monitored. Moreover, through in situ atomic force microscopy, the kinetic transition between α and δ phase is revealed to be the "nucleation-growth transition" process. Density functional theory calculation implies an enthalpy-driven α-to-δ degradation process during humidity aging and an entropy-driven δ-to-α healing process at high temperatures. The α phase of FA1- x Csx PbI3 can be stabilized at elevated temperature under high humidity due to the increased nucleation barrier, and the resulting non-encapsulated PSCs retain >90% of their initial efficiency after >1000 h at 60 °C and 60% relative humidity. This finding provides a deepened understanding on the phase-transition process of FA1- x Csx PbI3 from both thermodynamics and kinetics points of view, which also presents an effective means to stabilize the α phase of FA-dominated perovskites and devices for practical applications.

Enhanced Air and Electrochemical Stability of Li7P2.9Ge0.05S10.75O0.1 Electrolytes with High Ionic Conductivity for Thiophosphate-Based All-Solid-State Batteries.

Sulfide solid electrolytes (SSEs) show tremendous potential to realize high-energy-density secondary batteries and offer distinguishing safety features over the traditional liquid-electrolyte-based system. However, their installation is hindered by the air sensitivity and substandard interfacial compatibility with Li-metal anodes. Herein, an aliovalent P5+/Ge4+ and isovalent S2-/O2- cosubstitution strategy increases the σLi+ to 4.77 mS cm-1, which is associated with the lowest activation energy (18.66 kJ mol-1). Impressively, with limited substitution of P/Ge and S/O in Li7P3S11, the derived electrolytes largely suppressed the structural hydrolysis in the air. Furthermore, the Li//Li cell with novel Li7P2.9Ge0.05S10.75O0.1 SSEs realized Li plating/stripping over 100 h at 0.1 mA cm-2/0.1 mAh cm-2 @ RT, with the lowest overpotential at ∼5 mV. Next, ex situ X-ray photoelectron spectroscopy (XPS) quantified the electrochemical decomposition of the Li7P3S11/LiNbO3@NCA interface during cell operation. XPS results confirmed better thermodynamic stability between LiNbO3@NCA and L7P3S11 after GeO2 substitution. Accordingly, the LiNbO3@NCA/Li7P2.9Ge0.05S10.75O0.1/Li-In cell performed remarkably; first discharge capacity, 158.9 mAh g-1; capacity retention, 89%; and Coulombic efficiency, ∼100% after 50 cycles @ 0.064 mA cm-2 and even at 0.3 mA cm-2 versus the first discharge capacity and retention (129.4 mAh g-1 and 75.73%) after 70 cycles @ RT. These remarkable results could be attributable to the excellent σLi+, chemical/electrochemical stability toward LiNbO3@NCA, and meager interfacial resistance, essential for the practical application of sulfide-based batteries.

Surface-capping engineering for electrically neutral surface of perovskite films and stable solar cells.

Metal halide perovskite solar cells (PSCs) have developed rapidly in recent years, due to their high performance and low-cost solution-based fabrication process. These excellent properties are mainly attributed to the high defect tolerance of polycrystalline perovskite films. Meanwhile, these defects can also facilitate ion migration and carrier recombination, which cause the device performance and the long-term stability of PSCs to deteriorate heavily. Therefore, it is critical to passivate the defects, especially at the surfaces of perovskite grains where the defects are most concentrated due to the dangling bonds. Here we propose a surface-capping engineering (SCE) method to construct 'dangling-bond-free' surfaces for perovskite grains. Diamine iodide (methylenediammonium diiodide, MDAI2) was used to construct an electroneutral PbX6-MDA-PbX6(X = Cl, Br or I) layer at the perovskite surfaces. Compared to the monovalent FA+which can only coordinate one [PbX6]4-slab, the bivalent MDA2+can coordinate two [PbX6]4-slabs on both sides, thus realizing a dangling-bond-free surface. Solar cells based on SCE-perovskite films exhibited a higher power conversion efficiency (PCE) of 21.6%, compared with 19.9% of the control group; and maintained over 96% of its initial PCE after 13 h during the maximum power point tracking test under continuous AM1.5G illumination, whereas the control group only lasted 1.5 h. Constructing a dangling-bond-free capping layer on the grain boundary opens new avenues for the fabrication of ultralow-defect polycrystalline semiconductors, paving the way to further improve the PCE and lifetime of PSCs.

Dual-Layered Interfacial Evolution of Lithium Metal Anode: SEI Analysis via TOF-SIMS Technology.

Lithium metal battery has been considered as one of the most promising candidates for the next generation of energy storage systems due to its high energy density. However, the lithium metal may react with the electrolyte, resulting in the instability of the solid/liquid interface. The solid electrolyte interface (SEI) layer was found to affect the interface stability of the lithium metal anode; the real structure of SEI couldn't be accurately analyzed so far. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) has been thought as a powerful tool to carry out three-dimensional (3D) characterization and structural reconstruction at a high-resolution nanoscale, as well as detect ionized elements and molecule fragments at the ppb level due to its excellent sensitivity. Herein, we employed TOF-SIMS to investigate the chemical composition of SEI at the surface of the lithium metal anode after electrochemical cycles. We find that SEI is not a completely dense interface layer. The organic phase of SEI can accommodate part of the electrolyte, enhancing the lithium-ion conductivity. Meanwhile, SEI is an interface layer that changes with the state of the electrolyte, and this process of change is expressed by conventional characterization methods. However, the distribution of lithium salt can be analyzed by TOF-SIMS to judge the change degree of SEI. Our work provides significant guidance for accurately characterizing the SEI layer, as well as constructing a more realistic interface layer model.

Avoiding Structural Collapse to Reduce Lead Leakage in Perovskite Photovoltaics.

Perovskite solar cells (PSCs) have become a promising candidate for the next-generation photovoltaic technologies. As an essential element for high-efficiency PSCs however, the heavy metal Pb is soluble in water, causing a serious threat to the environment and human health. Due to the weak ionic bonding in three-dimensional (3D) perovskites, drastic structure decomposition occurs when immersing the perovskite film in water, which accelerates the Pb leakage. By introducing the chemically stable Dion-Jacobson (DJ) 2D perovskite at the 3D perovskite surface, the film dissolution is significantly slowed down, which retards lead leakage. As a result, the Pb contamination is dramatically reduced under various extreme conditions. In addition, the PSCs device deliver a power conversion efficiency (PCE) of 23.6 % and retain over 95 % of their initial PCE after the maximum power point tracking for over 1100 h.