Excellent Air Stability Research Articles

Preparation and degradation of high air stability sulfide solid electrolyte 75Li2S·25P2S5 glass-ceramic

The development of next-generation lithium-ion batteries relies heavily on the design and manufacture of solid electrolytes with excellent ionic conductivity and air stability. 75Li2S·25P2S5 glass-ceramic is a desirable and promising solid-electrolyte material, but further research is needed to understand how certain synthesis factors affect the local structure and ionic conductivity of the material. In addition, the majority of the existing research on the air stability of solid electrolytes simply record the change in the amount of H2S released over time, which is insufficient. Herein, we highlight the impact of a range of conditions in the ball milling stage (including jar filling factor, rotation speed, ball-to-powder ratio and total milling time) and the calcination stage (including heat-treatment temperatures and heat-treatment durations) on the 75Li2S·25P2S5 glass-ceramic synthesis, through powder X-ray diffraction, Raman and electrochemical impedance spectroscopy. We have found that this material has a relatively high air stability under optimal synthesis situations, taking approximately 6.5 min to release 5 ppm H2S. In addition, we present degradation studies on 75Li2S·25P2S5 glass-ceramic by electrochemical impedance spectroscopy, scanning electron microscope, energy dispersive spectroscopy and Raman. After being exposed to air for a period of time, the ionic conductivity of 75Li2S·25P2S5 glass-ceramic significantly decreased, and its morphology and structure were severely deteriorated. It is most likely that the sample eventually generates a mixture of Li3PO4, Li2SO4 and S8.

A one-dimensional conductive metal-organic framework with extended π-d conjugated nanoribbon layers

Conductive metal-organic frameworks (MOFs) have performed well in the fields of energy and catalysis, among which two-dimensional (2D) and three-dimensional (3D) MOFs are well-known. Here, we have synthesized a one-dimensional (1D) conductive metal-organic framework (MOF) in which hexacoordinated 1,5-Diamino-4,8-dihydroxy-9,10-anthraceneedione (DDA) ligands are connected by double Cu ions, resulting in nanoribbon layers with 1D π-d conjugated nanoribbon plane and out-of-plane π-π stacking, which facilitates charge transport along two dimensions. The DDA-Cu as a highly conductive n-type MOF has high crystalline quality with a conductivity of ~ 9.4 S·m−1, which is at least two orders of magnitude higher than that of conventional 1D MOFs. Its electrical band gap (Eg) and exciton binding energy (Eb) are approximately 0.49 eV and 0.3 eV, respectively. When utilized as electrode material in a supercapacitor, the DDA-Cu exhibits good charge storage capacity and cycle stability. Meanwhile, as thse active semiconductor layer, it successfully simulates the artificial visual perception system with excellent bending resistance and air stability as a MOF-based flexible optoelectronic synaptic case. The controllable preparation of high-quality 1D DDA-Cu MOF may enable new architectural designs and various applications in the future.

Hydrogen‐Assisted Synthesis of Large‐Size 2D Bismuth Telluride Flakes for Broadband Photodetection up to 2 µm

AbstractBroadband photodetection including optical communication wavelength band is of great significance because of the great potential for various civilian and military applications. Topological insulators with unique surface electronic states have attracted more and more attention in broadband photodetection. Among them, due to its suitable band gap (0.16–1.36 eV), ultra‐high mobility, and excellent air stability, 2D bismuth telluride (Bi2Te3) is regarded as a promising candidate. However, the growth of large‐size Bi2Te3 is challenging because of the poor chemical reactivity of tellurium (Te) element. Here, large‐scale (240 µm, ten times larger than the current record) Bi2Te3 flakes with controllable thickness (one to few layers) are successfully synthesized by H2‐assisted chemical vapor deposition. Thanks to the strong reducibility and the passivation on the substrate of H2, the growth rate is as high as 48 µm min−1, which is ten times faster than that reported. Moreover, the Bi2Te3‐photodetector exhibits broadband detection (520–2000 nm), high responsivity of 252 A W−1, excellent detectivity of 5.1 × 1011 cm Hz1/2 W−1, and fast response time (τrise/τdecay ≈ 41/38 ms), implying potential applications in broadband optoelectronics. More importantly, this work may pave a way for the rapid growth of other novel large‐scale 2D materials.

A novel garnet-type high-entropy oxide as air-stable solid electrolyte for Li-ion batteries

Li-ion batteries are considered prospective candidates for storage systems because of their high energy density and long cycling life. However, the use of organic electrolytes increases the risk of explosion and fire. Hence, all-solid-state Li-ion batteries have attracted considerable attention because the use of solid electrolytes avoids the combustion of electrolytes and explosions, and enhances the performance of batteries. Garnet-type oxides are commonly used solid electrolytes. The common Ta-doped Li7La3Zr2O12 can react easily with CO2 and H2O in air, and its ionic conductivity decays after contact with air. In this study, a novel garnet-type, high-entropy oxide, Li6.4La3Zr0.4Ta0.4Nb0.4Y0.6W0.2O12 (LLZTNYWO), is successfully synthesized as a solid electrolyte for Li-ion batteries,using a conventional solid-state method. Ta, Nb, Y, and W are used as substitutes for Zr, which significantly increase conductivity, have high stability in air, and a lower sintering temperature. LLZTNYWO achieves higher Li-ion conductivity at 1.16 × 10−4 S cm−1 compared to mono-doped Li6.6La3Zr1.6Ta0.4O12 (6.57 × 10−5 S cm−1), Li6.6La3Zr1.6Nb0.4O12 (2.19 × 10−5 S cm−1), and Li6.2La3Zr1.6W0.4O12 (1.16 × 10−4 S cm−1). Additionally, it exhibits higher ionic conductivity compared to equimolar Li5.8La3Zr0.4Ta0.4Nb0.4Y0.4W0.4O12 (1.95 × 10−5 S cm−1). The Li-ion conductivity of LLZTNYWO remains constant for 30 days in the atmosphere without decay, thereby revealing its excellent air stability. Furthermore, LLZTNYWO exhibits a remarkable electrochemical window of up to 6 V vs Li/Li+ and excellent electrochemical stability against Li metal after cycling at 0.1 mA·cm−2 for 2 h, which indicates that it is a promising solid electrolyte for Li-ion batteries.

Rapidly Photocurable Solid-State Poly(ionic liquid) Ionogels For Thermally Robust and Flexible Electrochromic Devices.

Formation of ionogels through in situ polymerization can effectively improve electrolyte processability; however, the curing process has been slow and oxygen-sensitive. Considering the low oxygen solubility of poly(ionic liquid)s (PILs), in situ polymerized ionogels are designed to realize excellent electrolytes. Herein, two in situ polymerized ionogels (PIL A & PIL B) are formulated, and they can be rapidly photocured within a minute. The ionogels are highly transparent, stretchable, and exhibit excellent physicochemical stability, including thermal, electrochemical, and air stability, allowing them to perform in various conditions. Benefitting from these properties, two high-performance electrochromic devices (ECDs) are assembled, with iron-centered coordination polymer (FeCP) and tungsten oxide (P-WO3 ) electrochromic materials, achieving high color contrast (45.2% and 56.4%), fast response time (1.5/1.9 and 1.7/6.4 s), and excellent cycling endurance (>90% retention over 3000 cycles). Attributed to the thermal robustness of the ionogels, the ECDs can also be operated over a wide temperature range (-20 to 100 °C). With the use of deformable substrates (e.g., ultrathin ITO glass), curved electrochromic eye protector and flexible electrochromic displays are realized, highlighting their potential use in futuristic wearables.

Artificially transformed ultra-stable Li6.75La3Zr1.75Ta0.25O12 incorporated composite solid electrolyte towards high voltage solid lithium metal batteries

Garnet-type Li6.75La3Zr1.75Ta0.25O12 (LLZTO) is enlightening great future in solid-state lithium metal batteries due to the considerable ionic conductivity and good compatibility with metallic lithium. Unfortunately, LLZTO is always trapped into the Li2CO3 by-product forming on the surface in a moist atmosphere and becomes difficult for practical application. Herein, we propose an in-situ conversion from the Li2CO3 by-product towards electrochemical active LiCoO2 to turn this disadvantage. The modified LLZTO (M−LLZTO) realizes excellent air stability and performs impressively enhanced electrochemical performance in the structure application of both cathode and composite solid electrolyte (CSE). The prepared CSE delivers high ionic conductivity and good electrochemical stability against Li metal with an ultra-long lifespan over 2000 h in the symmetrical cells. Once working in a solid-state lithium battery with a LiCoO2 cathode, the solid battery maintains a low capacity fade of 4.51 % over 150 cycles and a high average columbic efficiency of 99 %. All these results promise a new insight into the air sensitive solid electrolyte for advanced solid-state lithium batteries.

Aqueous synthesis of stable Zn alloyed manganese halides for efficient backlit display

Metal halide perovskite has been widely researched in the field of wide color gamut backlight due to its excellent luminescence properties. However, the toxicity of lead and thermal stability issue greatly hindered its practical application. In this regard, environmentally friendly manganese halide perovskites has intrigued great attention. Herein, facile yet robust preparation of highly emissive all-inorganic manganese halides is presented via a one-step pure aqueous solution-based method without using corrosive acid solution. The introduction of Zn2+ cation-alloying enables the weakly luminescent Cs3MnCl5 to exhibit exceptionally efficient green emission at 521 nm. The alloyed Cs3MnxZn(1-x)Cl5 exhibits superior optical properties as well as improved thermal stability. In particular, alloyed Cs3MnxZn(1-x)Cl5 still retained 74% of the initial fluorescence intensity when the heating temperature was raised up to 225 °C. Furthermore, within the protective encapsulation of polydimethylsiloxane (PDMS) matrix, the prepared Cs3MnxZn(1-x)Cl5@PDMS films demonstrates excellent air, water and blue-light stability, which can be readily applied as light conversion films in backlit display. The as-prepared Cs3MnxZn(1-x)Cl5@K2SiF6: Mn4+@PDMS films displayed excellent quality and the color gamut was over 113% of the NTSC 1953 standard. This work provides a simple and effective pure aqueous-based strategy for the development of environment-friendly perovskite materials for the application of wide color gamut backlit display.

Two-Dimensional Electron Gas in MoSi2N4/VSi2N4 Heterojunction by First Principles Calculation

Van der Waals (vdW) layered two-dimensional (2D) materials, which may have high carrier mobility, valley polarization, excellent mechanical properties and air stability, have been widely investigated before. We explore the possibility of producing a spin-polarized two-dimensional electron gas (2DEG) in the heterojunction composed of insulators MoSi2N4 and VSi2N4 by using first-principles calculations. Due to the charge transfer effect, the 2DEG at the interface of the MoSi2N4/VSi2N4 heterojunction is found. Further, for different kinds of stacking of heterojunctions, lattice strain and electric fields can effectively tune the electronic structures and lead to metal-to-semiconductor transition. Under compressive strain or electric field parallel to c axis, the 2DEG disappears and band gap opening occurs. On the contrary, interlayer electron transfer enforces the system to become metallic under the condition of tensile strain or electric field anti-parallel to c axis. These changes are mainly attributed to electronic redistribution and orbitals’ reconstruction. In addition, we reveal that MoSi2N4/VSi2N4 lateral heterojunctions of armchair and zigzag edges exhibit different electronic properties, such as a large band gap semiconductor and a metallic state. Our findings provide insights into electronic band engineering of MoSi2N4/VSi2N4 heterojunctions and pave the way for future spintronics applications.

Stability of LiNi0.8Co0.15Al0.05O2 structure in air and H2 atmospheres at elevated temperatures

LiNi0.8Co0.15Al0.05O2 (LNCA), which is a typical electrode material used in lithium ion batteries, has recently been applied as electrodes for ceramic fuel cells (CFCs). However, the stability of LNCA under CFC operating conditions (i.e., oxidative/reductive atmospheres and elevated temperatures) remains unknown. Herein, we evaluated the structure change of LNCA in air and H2 atmospheres at elevated temperatures. It was found that LNCA exhibited excellent stability in ambient air within a wide temperature range from room temperature to 800 °C. However, the H2 atmosphere caused the decomposition of LNCA into LiOH and NiO/CoO solid solution at 300 °C, followed by complete reduction to Ni/Co alloy at 600 °C. The H2-promoted decomposition is a near second order reaction with activation energy of 223.59 kJ mol−1. These findings indicate that LNCA can be used as a stable cathode and it is a suitable precursor for the in-situ formation of Ni/Co-based anodes for CFCs.

Screen-Printable Cu–Ag Core–Shell Nanoparticle Paste for Reduced Silver Usage in Solar Cells: Particle Design, Paste Formulation, and Process Optimization

Copper–silver (Cu–Ag) core–shell nanoparticles are promising for replacing the silver particles and flakes used in printed conductors in current solar cells since they deliver good conductivity, chemical stability, and optical performance, while also reducing the silver content, thus significantly impacting the cost. The bare nanoparticles offer excellent air stability thanks to the silver-covered copper structure. We demonstrate a screen-printable paste for use in solar cell conductor applications. We report a printed morphology and light reflection properties similar to those achieved with commercial silver pastes. The reported Cu–Ag core–shell paste is uniquely formulated with an epoxy binder and an aliphatic hardener, delivering significantly improved electrical conductivity, while simultaneously reducing the overall silver content by ∼36 wt %. This is attributable to the cross-linked polymeric structure, low-temperature conversion, and improved loading of conductive core–shell nanoparticles. As needed for contact formation in conventional top-contact silicon solar cells, the paste is additionally loaded with lead bisilicate and delivers conductivity on par with that of commercial silver paste. Thus, by combining the reduction of the silver content with excellent electronic and optical properties, this Cu–Ag nanoparticle-based paste becomes attractive for low-cost printed-conductor applications, including photovoltaics and electronics.

Lead-free zero-dimensional Cs2ZnBr4 perovskite single crystals with broadband emission covering visible spectrum

All-inorganic lead-free zero-dimensional (0D) metal halides perovskites with intriguing photoluminescent (PL) properties have aroused much interest due to their application in lighting and artificial illumination. Herein, 0D Cs2ZnBr4 perovskite single crystals were synthesized through simple solvothermal method. The phase purity, the electronic band structure and electronic density of states of Cs2ZnBr4 are investigated by X-ray diffraction (XRD) measurement and density functional theory (DFT) calculation. Under 430 nm blue light excitation, Cs2ZnBr4 single crystals exhibit broadband emission covering the visible region from 450 to 750 nm and large Stokes shift about 120 nm, originating from self-trapped excitons (STEs) radiative recombination. And Cs2ZnBr4 shows excellent thermal and air stability. These results indicate the potential application of Cs2ZnBr4 as environmental-friendly light emitters for solid state lighting and displaying.

Excellent flame retardancy and air stability through surface coordination of few‐layer black phosphorus with TiL4 in epoxy resin

AbstractBlack phosphorus (BP) has been attractive for many research groups as its promising properties. However, the poor air stability of BP has limited its practical applications. To simultaneously address this problem and improve the flame retardancy of BP in epoxy resin (EP), a surface coordination strategy was proposed. Herein, a titanium ligand (denoted as TiL4) was designed to coordinate BP nanosheets, which can occupy the lone pair electrons of BP. The Ti–P coordination contributed to the improvement of ambient stability of BP. The serious degradation was observed from pure BP owing to the oxidation. Whereas, the surface coordination can impede the ambient degradation rate of BP by 74.07%. With the addition of 1.5 wt% TiL4@BP, the char yield of EP nanocomposites was increased by 20.55% due to the catalytic charring effect of TiL4@BP. The incorporation of 1.5 wt% TiL4@BP can reduce the peak of heat release rate and total heat release values of EP by 29.41% and 23.32%. The EP/TiL4@BP 1.5 also can pass the UL‐94 V‐0 rating, and its value of limiting oxygen index was enhanced by 13.60%. The improvement in the flame retardancy of BP in EP can be largely ascribed to synergistic catalytic charring effects between BP and TiL4. The condense and compact char layer can act as a physical barrier to restrict the exchange of pyrolytic products and the transfer of heat. In addition, the free radical quenching effect of BP nanosheets also accounted for the excellent flame retardant performance of EP. This work proposed a reference for synchronically obtaining the improvement for the air stability and flame retardant performance of BP.

High‐Performance Visible to Near‐Infrared Broadband Bi2O2Se Nanoribbon Photodetectors

AbstractOwing to its suitable electronic bandgap, excellent air stability, and high carrier mobility at room temperature, low‐dimensional bismuth oxyselenide (Bi2O2Se) has become attractive in the context of visible–near‐infrared (VIS–NIR) detection. However, the high carrier concentration and bolometric effect of Bi2O2Se nanosheets are not conducive to reducing the dark current and improving the response speed, which hinders Bi2O2Se nanosheet‐based photodetectors from achieving an optimal performance. In this study, a Bi2O2Se nanoribbon is controllably synthesized on a fluorophlogopite substrate by means of the chemical vapor deposition approach. Through the use of a Bi2O2Se nanoribbon structure and the application of a Schottky barrier between the Bi2O2Se and Au electrodes, a fast response and low noise photodetector is achieved. More specifically, the response times are 2.1 and 313 µs at 650 and 1550 nm, respectively, and the corresponding optimal detectivities are 3.28 × 1013 and 8.07 × 109 Jones. Furthermore, the device reaches a −3 dB bandwidth of 81 kHz and exhibits a responsivity of 3.2 × 105 A W−1 at 650 nm under a bias of 5 V. This study provides new opportunities for the application of high‐performance VIS–NIR photodetectors.

Photoelectrocatalytic CO2 reduction using stable lead-free bimetallic CsAgBr2 halide perovskite nanocrystals

• Rietveld refinement confirming the orthorhombic phase of CsAgBr 2 perovskite nanocrystals with space group Cmcm. • Crystalline nature of the CsAgBr 2 nanocrystals exhibiting photocatalytic CO 2 reduction. • High structural stability displayed by CsAgBr 2 nanocrystals (no degradation up to 6 months) in ambient conditions. • Thermally stable without loss of structural configuration up to 200 °C. • Superior photocatalytic CO 2 reduction with a CO yield ∼14 μmol g −1 h −1 and 50% Faradic efficiency. We report on the fabrication and systematic characterization of highly stable lead-free CsAgBr 2 perovskite nanocrystals (PNC) processed at room temperature without the involvement of any organic ligand. X-ray diffraction (XRD) measurements and Rietveld analysis of the data reveal that the synthesized perovskites are in the orthorhombic phase with space group Cmcm . The optical properties of the CsAgBr 2 PNC are analyzed by UV–Vis absorbance and photoluminescence spectra. Morphological studies are performed by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Additionally, the high degree of structural stability of the PNC was reaffirmed by time-dependent XRD profiles, and the thermal stability was studied by Thermogravimetric analysis (TGA). PNC exhibit excellent air stability for up to six months and thermal stability up to 200 °C. Furthermore, we demonstrate superior photoelectrocatalytic CO 2 reduction using CsAgBr 2 PNC with around ∼14 μmol g −1 h −1 of CO yield and 50% Faradic efficiency.

Ti3C2Tx MXene/urchin-like PANI hollow nanosphere composite for high performance flexible ammonia gas sensor

Ammonia (NH3) has been used as a typical indicator to monitor food spoilage, human health, and air quality. However, the development of flexible NH3 sensors with high response, excellent selectivity and low cost remains a huge challenge. Herein, a high performance NH3 sensor based on Ti3C2Tx MXene nanosheet/urchin-like PANI hollow nanosphere composite (MP) was fabricated through template method and in situ polymerization. The NH3 sensor is fabricated with no high cost electrodes through directly depositing this composite on flexible polyethylene terephthalate (PET) during polymerization. This optimized MP film sensor exhibits high response of 3.70 to 10 ppm NH3 at room temperature, which is 4.74-fold in comparison with urchin-like PANI hollow nanosphere (u-PANI). It also shows excellent selectivity, good repeatability, satisfactory flexibility, air stability and low detection limit of 30 ppb. The effective morphology control and heterojunction construction of MP composite are responsible for superior sensing performance. Moreover, the application of this film sensor in the monitoring of the spoilage process of fresh pork is demonstrated. This study offers a new strategy for fabricating high performance flexible room-temperature NH3 sensors, which may be scale fabrication and application in daily life.

Simultaneous exfoliation and functionalization of black phosphorus by sucrose-assisted ball milling with NMP intercalating and preparation of flame retardant polyvinyl alcohol film

Recently, layered black phosphorus (BP) has become a rising star in two-dimensional materials because of high thermal stability, excellent mechanical properties, and size effect. Layered BP can be used as an ideal filler for the preparation of polymer-based composites with high performance. Realizing the exfoliation and functionalization of BP has become the key to BP's application. Under the protection of N-methylpyrrolidone (NMP) and the assistance of sucrose, we completed the preparation and functionalization of layered BP by ball milling. Surface grafting of oxygen-containing functional groups can realize the uniform dispersion of BP in matrix and improve its stability in air. As expected, the nanocomposites prepared by adding sucrose grafted BP into polyvinyl alcohol (PVA) matrix have significantly improved flame retardancy and mechanical strength. When the addition amount of BP-sucrose(N) was 5 wt%, compared with pure PVA, the decrease of the peak heat release rate (PHRR) and total heat release (THR) reached 52.5% and 32.8%, and the tensile strength increased by 131.2%. Moreover, the addition of NMP can avoid the excessive destruction of the two-dimensional crystal structure of BP, which can also improve the performance of nanocomposites. Due to the encapsulation effect of sucrose, the nanocomposites have excellent air stability. The Ag1/Ag2 value only decreases from 0.52 to 0.49 even after three months of exposure to environmental conditions, which proves that the degree of oxidation is low. This work has provided an efficient way to exfoliate and functionalize BP simultaneously, and expanded the application of BP in flame retardant nanocomposites.

A high mobility air-stable n-type organic small molecule semiconductor with high UV–visible-to-NIR photoresponse

An organic semiconductor with high carrier mobility and efficient light absorption over a wide spectral range is of the most important yet challenging material for constructing a broadband responsive organic photodetector. However, the development of such organic semiconductors, especially for air-stable n-type organic small molecule semiconductors, is still at an early stage. Here we report the fabrication of high-performance n-type semiconducting crystalline nanosheets and the development of air-stable field-effect transistors, phototransistors, with high response over a broad spectrum. The n-type small molecule semiconductor is assembled into a crystalline nanosheet based on the solvent-phase interfacial self-assembly method. N-type field-effect transistors with high electron mobility are fabricated and their electrical performances exhibit excellent air stability. Impressively, the demonstrated phototransistors exhibit an ultrahigh responsivity over a wide spectral range from 365 to 940 nm, with a maximum photoresponsivity of 9.2 × 105 A W−1 and specific detectivity of 5.26 × 1013 Jones, which is the best performance among the reported n-type organic small molecule-based phototransistors.

Hydrazide Derivatives for Defect Passivation in Pure CsPbI3 Perovskite Solar Cells.

All-inorganic CsPbI3 perovskite presents preeminent chemical stability and a desirable band gap as the front absorber for perovskite/silicon tandem solar cells. Unfortunately, CsPbI3 perovskite solar cells (PSCs) still show low efficiency due to high density of defects in solution-prepared CsPbI3 films. Herein, three kinds of hydrazide derivatives (benzoyl hydrazine (BH), formohydrazide (FH) and benzamide (BA)) are designed to reduce the defect density and stabilize the phase of CsPbI3 . Calculation and characterization results corroborate that the carboxyl and hydrazine groups in BH form strong chemical bonds with Pb2+ ions, resulting in synergetic double coordination. In addition, the hydrazine group in the BH also forms a hydrogen bond with iodine to assist the coordination. Consequently, a high efficiency of 20.47 % is achieved, which is the highest PCE among all pure CsPbI3 -based PSCs reported to date. In addition, an unencapsulated device showed excellent stability in ambient air.

Hydrazide Derivatives for Defect Passivation in Pure CsPbI3 Perovskite Solar Cells

AbstractAll‐inorganic CsPbI3 perovskite presents preeminent chemical stability and a desirable band gap as the front absorber for perovskite/silicon tandem solar cells. Unfortunately, CsPbI3 perovskite solar cells (PSCs) still show low efficiency due to high density of defects in solution‐prepared CsPbI3 films. Herein, three kinds of hydrazide derivatives (benzoyl hydrazine (BH), formohydrazide (FH) and benzamide (BA)) are designed to reduce the defect density and stabilize the phase of CsPbI3. Calculation and characterization results corroborate that the carboxyl and hydrazine groups in BH form strong chemical bonds with Pb2+ ions, resulting in synergetic double coordination. In addition, the hydrazine group in the BH also forms a hydrogen bond with iodine to assist the coordination. Consequently, a high efficiency of 20.47 % is achieved, which is the highest PCE among all pure CsPbI3‐based PSCs reported to date. In addition, an unencapsulated device showed excellent stability in ambient air.

High output mode-locked laser empowered by defect regulation in 2D Bi2O2Se saturable absorber

Atomically thin Bi2O2Se has emerged as a novel two-dimensional (2D) material with an ultrabroadband nonlinear optical response, high carrier mobility and excellent air stability, showing great potential for the realization of optical modulators. Here, we demonstrate a femtosecond solid-state laser at 1.0 µm with Bi2O2Se nanoplates as a saturable absorber (SA). Upon further defect regulation in 2D Bi2O2Se, the average power of the mode-locked laser is improved from 421 mW to 665 mW, while the pulse width is decreased from 587 fs to 266 fs. Moderate Ar+ plasma treatments are employed to precisely regulate the O and Se defect states in Bi2O2Se nanoplates. Nondegenerate pump-probe measurements show that defect engineering effectively accelerates the trapping rate and defect-assisted Auger recombination rate of photocarriers. The saturation intensity is improved from 3.6 ± 0.2 to 12.8 ± 0.6 MW cm−2 after the optimized defect regulation. The enhanced saturable absorption and ultrafast carrier lifetime endow the high-performance mode-locked laser with both large output power and short pulse duration.