Improved Moisture Stability Research Articles

Unravelling the O-doping effect on chemical/electrochemical stability of Li5.5PS4.5Cl1.5 for all-solid-state lithium batteries

Chlorine-rich Li-argyrodite sulfide solid electrolytes Li5.5PS4.5Cl1.5 are applied in all-solid-state batteries (ASSBs) due to the promising ionic transport and structural stability. However, the poor air/moisture stability and incompatibility to Li metal impede their practical applications. Herein, we synthesized a Li5.5PS4.5Cl1.5-based argyrodite exhibiting improved moisture stability and electrochemical performance to metallic Li, as well as high-voltage cathodes through O doping. The prepared oxygen-doped Li5.5PS4.5Cl1.5 samples (Li5.5PS4.425O0.075Cl1.5) possess significantly enhanced air stability and lower migration barrier in comparison with pristine Li5.5PS4.5Cl1.5. Moreover, Li5.5PS4.425O0.075Cl1.5 exhibits lower polarization voltage and better compatibility with lithium metal in the constant current charge-discharge tests of Li-Li symmetrical cell. This is attributed to the Cl-O coexistence coating interface that observed in the interface of Li/Li5.5PS4.425O0.075Cl1.5. To fully leverage the ultrafast ionic conductivity of Li5.5PS4.5Cl1.5, we construct ASSBs using optimized Li5.5PS4.425O0.075Cl1.5 as buffer layer between pristine LiNi0.6Mn0.2Co0.2O2 cathode materials and Li5.5PS4.5Cl1.5, leading to higher discharge capacities and elevated capacity retention. Based on above results, we further introduce LiNbO3-coated LiCoO2 as cathode, combined with Li5.5PS4.425O0.075Cl1.5 as an isolating layer between Li anode and Li5.5PS4.5Cl1.5 to suppress the growth of Li dendrite and achieve superior cyclability at wide voltage windows. Consequently, the all-solid-state lithium batteries exhibit promising application in a wide temperature range. This work provides a compelling strategy for achieving improved Chlorine-rich Li-argyrodite solid electrolytes with excellent air stability, high ionic conductivity and Li dendrite suppression capability, hence enabling all-solid-state batteries with high energy density and superior cyclability.

Quality of honey from Tubuna bees (Scaptotrigona bipunctata) fresh, thermally treated and during storage

Intrinsic characteristics, such as the presence of sugars and high levels of moisture and water activity, give stingless bee honey a greater tendency to fermentation than Apis mellifera honey. Thus, this study aimed to evaluate the physicochemical, microbiological, and antioxidant parameters of honey sourced from Tubuna bees (Scaptotrigona bipunctata) in its fresh state, following thermal treatment, and during storage. Samples were collected from three meliponaries in the South of Brazil. Thermal treatment involved a 3 min immersion at 65 °C, and storage occurred at ambient temperature. Parameters assessed included moisture, free acidity, pH, water activity, soluble solids, reducing sugars, apparent sucrose, hydroxymethylfurfural, color, ash, mesophilic aerobic bacteria, molds, yeasts, Escherichia coli, and antioxidant activity (DPPH and ABTS). Thermally treated honey demonstrated improved moisture stability, acidity, water activity, and increased color during storage. There were no significant differences in pH, soluble solids, hydroxymethylfurfural, bacteria, molds, yeasts, and antioxidant activity between thermally treated and fresh honey, and during storage. Both fresh and thermally treated S. bipunctata honey samples were free from E. coli and maintained values within state legislation limits for moisture, sugars, hydroxymethylfurfural, ash, molds, and yeasts during storage. However, the microorganism count was reduced, and an increase in antioxidant activity after 360 days was observed. The treatment in a water bath at 65 °C for 3 min preserved the physicochemical, microbiological, and antioxidant quality of Scaptotrigona bipunctata honey during storage. The results hold promise for supporting “meliponicultores”, offering market opportunities, ensuring product quality, and fostering sustainability while preserving local biodiversity and culture.

Wet Chemistry Route to Li3InCl6: Microstructural Control Render High Ionic Conductivity and Enhanced All-Solid-State Battery Performance.

Thanks to superionic conductivity and compatibility with >4V cathodes, halide solid electrolytes (SEs) have elicited tremendous interest for application in all-solid-state lithium batteries (ASSLBs). Many compositions based on groups 3, 13, and divalent metals, and substituted stoichiometries have been explored, some displaying requisite properties, but the Li+ conductivity still falls short of theoretical predictions and appealing sulfide-type SEs. While controlling microstructural characteristics, namely grain boundary effects and microstrain, can boost ionic conductivity, they have rarely been considered. Moving away from the standard solid-state route, here a scalable and facile wet chemical approach for obtaining highly conductive (>2 mS cm-1) Li3InCl6 is presented, and it is shown that aprotic solvents can reduce grain boundaries and microstrain, leading to very high ionic conductivity of over 4 mS cm-1 (at 22°C). Minimized grain boundary area renders improved moisture stability and enhances solid-solid interfacial contact, leading to excellent LiNi0.6Mn0.2Co0.2O2-based full-cell performance, exemplified by stable room temperature (22°C) cycling at a 0.2 C rate with 155 mAh g-1 capacity and 85% retention after 1000 cycles at 60°C with a high 99.75% Coulombic efficiency. The findings showcase the viability of the aprotic solvent-mediated route for producing high-quality Li3InCl6 for all-solid-state batteries.

Structural Diversity in 2-(2-Aminoethyl)pyridine-Based Lead Iodide Hybrids.

While 2D metal-organic hybrids have emerged as promising solar absorbers due to their improved moisture stability, their inferior transport properties limit their potential translation into devices. We report a new hybrid containing 2-(2-ammonioethyl)pyridine [(2-AEP)+], forming a 2D hybrid with the composition (2-AEP)2PbI4. The organic bilayer comprises of (2-AEP)+, which is arranged in a face-to-face stacking that promotes π-π interactions between neighboring pyridyl rings. We also demonstrate the structural diversity of 2-(2-aminoethyl)pyridine-based lead iodide hybrids in solution-processed films. This report highlights the importance of solution-processing conditions in trying to obtain single-phase films of hybrids containing dibasic organic species.

Arising 2D Perovskites for Ionizing Radiation Detection.

2D perovskites have greatly improved moisture stability owing to the large organic cations embedded in the inorganic octahedral structure, which also suppresses the ions migration and reduces the dark current. The suppression of ions migration by 2D perovskites effectively suppresses excessive device noise and baseline drift and shows excellent potential in the direct X-ray detection field. In addition, 2D perovskites have gradually emerged with many unique properties, such as anisotropy, tunable bandgap, high photoluminescence quantum yield, and wide range exciton binding energy, which continuously promote the development of 2D perovskites in ionizing radiation detection. This review aims to systematically summarize the advances and progress of 2D halide perovskite semiconductor and scintillator ionizing radiation detectors, including reported alpha (α) particle, beta (β) particle, neutron, X-ray, and gamma (γ) ray detection. The unique structural features of 2D perovskites and their advantages in X-ray detection are discussed. Development directions are also proposed to overcome the limitations of 2D halide perovskite radiation detectors.

Compound doping enables efficient CsPbBr3 nanocrystal light emitting diodes

All-inorganic cesium-based perovskite nanocrystals (PeNCs) attract much attentions in displays due to their facile synthesis protocol and superior luminous performance, while material instability hinders their practical applications. Herein, by inducing a multi-functional dopant, i.e., SrBr2, into the perovskite precursor solution, the as-formed SrBr2-doped CsPbBr3 NCs possess purer phases, suppressed defects and hydrophobic surfaces, which leads to a high photoluminescence quantum yield of ∼90 %, as well as much improved moisture stability. Benefiting from dopant passivation and improved luminescence properties, the doped CsPbBr3 light emitting diodes show five times and two times of current efficiency and external quantum efficiency improvements, respectively, in comparison to their undoped counterparts.

Resolving the Ultrafast Charge Carrier Dynamics of 2D and 3D Domains within a Mixed 2D/3D Lead‐Tin Perovskite

AbstractMixed 2D/3D perovskite materials are of particular interest to the photovoltaics and light‐ emitting diode (LED) communities due to their impressive opto‐electronic properties alongside improved moisture stability compared to conventional 3D perovskite absorbers. Here, a mixed lead‐tin perovskite containing distinct, self‐assembled domains of either 3D structures or highly phase‐pure Ruddlesden–Popper 2D structures is studied. The complex energy landscape of the material is revealed with ultrafast optical transient absorption measurements. It is shown that charge transfer between these microscale domains only occurs on nanosecond timescales, consistent with the large size of the domains. Using optical pump‐terahertz probe spectroscopy, the effective charge‐carrier mobility is shown to be an intermediary between analogous pure 2D and 3D perovskites. Furthermore, detailed analysis of the free carrier recombination dynamics is presented. By combining results from a range of excitation wavelengths within a full dynamic model of the photoexcited carrier population, it is shown that the 2D domains in the film exhibit remarkably similar carrier dynamics to the 3D domains, suggesting that long‐range charge‐transport should not be impeded by the heterogeneous structure of the material.

Low Bandgap 2D Perovskite Single Crystal with Anomalous-large Charges/ions Collection Ratio for Ultra-sensitive and Stable X-ray Detectors.

The low-dimensional halide perovskites have attracted increasing attention due to their improved moisture stability, reduced defects, and suppressed ions migration in many optoelectronic devices such as solar cells, light-emitting diodes, X-ray detectors, and so on. However, they are still limited by their large band gap and short charge carriers' diffusion length. Here, we demonstrate that the introduction of metal ions into organic interlayers of two-dimensional (2D) perovskite by cross-linking the copper paddle-wheel cluster-based lead bromide ([Cu(O2 C-(CH2 )3 -NH3 )2 ]PbBr4 ) perovskite single crystals with coordination bonds can not only significantly reduce the perovskite band gap to 0.96 eV to boost the X-ray induced charge carriers, but can also selectively improve the charge carriers' transport along the out-of-plane direction and blocking the ions motion paths. The [Cu(O2 C-(CH2 )3 -NH3 )2 ]PbBr4 single-crystal device can reach a record charges/ions collection ratio of 1.69×1018 ±4.7 % μGyair -1 s, and exhibit a large sensitivity of 1.14×105 ±7% μC Gyair -1 cm-2 with the lowest detectable dose rate of 56 nGyair s-1 under 120 keV X-rays irradiation. In addition, [Cu(O2 C-(CH2 )3 -NH3 )2 ]PbBr4 single-crystal detector exposed to the air without any encapsulation shows excellent X-ray imaging capability with long-term operational stability without any attenuation of 120 days.

Low Bandgap 2D Perovskite Single Crystal with Anomalous‐large Charges/ions Collection Ratio for Ultra‐sensitive and Stable X‐ray Detectors

AbstractThe low‐dimensional halide perovskites have attracted increasing attention due to their improved moisture stability, reduced defects, and suppressed ions migration in many optoelectronic devices such as solar cells, light‐emitting diodes, X‐ray detectors, and so on. However, they are still limited by their large band gap and short charge carriers’ diffusion length. Here, we demonstrate that the introduction of metal ions into organic interlayers of two‐dimensional (2D) perovskite by cross‐linking the copper paddle‐wheel cluster‐based lead bromide ([Cu(O2C−(CH2)3−NH3)2]PbBr4) perovskite single crystals with coordination bonds can not only significantly reduce the perovskite band gap to 0.96 eV to boost the X‐ray induced charge carriers, but can also selectively improve the charge carriers’ transport along the out‐of‐plane direction and blocking the ions motion paths. The [Cu(O2C−(CH2)3−NH3)2]PbBr4 single‐crystal device can reach a record charges/ions collection ratio of 1.69×1018±4.7 % μGyair−1 s, and exhibit a large sensitivity of 1.14×105±7% μC Gyair−1 cm−2 with the lowest detectable dose rate of 56 nGyair s−1 under 120 keV X‐rays irradiation. In addition, [Cu(O2C−(CH2)3−NH3)2]PbBr4 single‐crystal detector exposed to the air without any encapsulation shows excellent X‐ray imaging capability with long‐term operational stability without any attenuation of 120 days.

Regulating structural asymmetry via fluorination engineering in hybrid lead bromide perovskites.

Here, we synthesized a pair of chiral two-dimensional lead bromide perovskites R-/S-(C3H7NF3)2PbBr4 (1R/2S) using a H/F substitution strategy, which exhibit circular dichroism (CD) and circularly polarized luminescence (CPL) activity. Compared with one-dimensional non-centrosymmetric (C3H10N)3PbBr5 with local asymmetry obtained by isopropylamine, 1R/2S show a centrosymmetric inorganic layer despite the global chiral space group. Density functional theory calculations show that the formation energy of 1R/2S is lower than that of (C3H10N)3PbBr5, which implies the improved moisture stability in photophysical properties and CPL activity.

Divalent organic cations as a novel protective layer for perovskite materials

Modifying the surface of perovskite MAPbI3with a lying chain-like divalent organic cation to improve moisture stability.

Water-assistant ultrahigh fluorescence enhancement in perovskite polymer-encapsulated film for flexible X-ray scintillators

Methylammonium lead halide perovskites are well-known having a poor stability towards moisture. Water causes degradation of ionic perovskites and weaken the optical and electronic performance of perovskite-based devices. Main strategies to improve moisture stability are compositional engineering, surface engineering and matrix encapsulation. Herein, encapsulation strategy is implemented through screening a polymer matrix, a hydrophobic room-temperature vulcanized silicone rubber (RTV-2). Owing to the positive effect of moderate water on the performance of perovskites, the obtained MAPbBr3/RTV-2 composite film is processed with water post-treatment to undergo surface engineering. The composite film achieves a remarkable 8-fold fluorescence enhancement. Luminous efficiency of the film loaded on a 380 nm chip is improved from 51.4 lm/W to 135.37 lm/W. The flexible MAPbBr3/RTV-2 film responds sensitively under X-ray irradiation. Its detection limit is down to 12 nGyair s−1, 400 times lower than the regular dosage in X-ray diagnostics (5.5 μGy s−1). These results provide guidance to design perovskite-based devices with bright luminescence and excellent flexibility to qualify the wearable X-ray detectors for dose monitoring.

Hydrogen-iodide bonding between glycine and perovskite greatly improve moisture stability for binary PSCs

In recent years, the maximum power conversion efficiency (PCE) of perovskite solar cells (PSCs) has exceeded 25%. However, stability, especially under high relative humidity, has become a great obstacle for commercialization of perovskite devices due to its intrinsic defects. Interface modification is an effective method to improve the performance of PSCs for it could validly restrain defects and prevent decomposition of perovskite. In this paper, interface properties have been greatly improved by glycine (GLY) doped SnO 2 electron transport layer (ETL) in planar binary PSCs. SnO 2 -GLY ETL leads to improved band alignment, reduced charge recombination and enhanced electron mobility. XPS and NMR results demonstrate that the ammonia group in GLY combined with perovskite through hydrogen-iodide bonding, which greatly improves the moisture stability of the devices. The best PCE of the perovskite solar cell increased from 19.08% to 21.18%, and GLY modified devices can maintain 88% of its initial PCE after 7 days under 60 ± 5% relative humidity (RH) in ambient condition without any encapsulation. While, thermal stability test results indicating that hydrogen bonding is just a little helpful for improving stability at high temperature. This work indicates that forming hydrogen bonding between perovskite and ETL is an effective way to enhance moisture stability for commercialization of PSCs. • Interface properties between SnO 2 ETL and PSCs are improved by glycine (GLY), leading to enhanced PCE from 19.11% to 21.18%. • The amino group in GLY is bound to perovskite by hydrogen iodide bond, which greatly improves water stability of the device. • Long-term and thermal stability of the devices have also been improved.

Synergistic effect of guanidinium tetrafluoroborate boosting photovoltaic performance of perovskite solar cells

The power conversion efficiency (PCE) of the perovskite solar cell (PSC) has made an illustrious breakthrough in the past ten years. However, it is still a great challenge to fabricate high-quality perovskite films due to the intrinsic high defect-density and internal non-radiative recombination, which has severely hindered the development of PSCs. Herein, a new-type additive guanidinium tetrafluoroborate (GuaBF4) is introduced to improve the perovskite films quality, thus boosting photovoltaic performance of resultant PSCs. It is demonstrated that owing to the synergistic effect of Gua+ and BF4−, the introduction of GuaBF4 can improve the quality of CH3NH3PbI3 (MAPbI3) films. Through optimizing the concentration of GuaBF4, the MAPbI3 film with GuaBF4 displays higher crystallinity, enlarged crystal grain and smoother surface. Furthermore, by virtue of the strong interaction between MAPbI3 and GuaBF4, the inclusion of GuaBF4 can effectively passivate traps/defects in perovskite films, thereby diminishing the non-radiative recombination and promoting the charge carrier transportation. Consequently, a high-performance MAPbI3 PSC with a PCE of 20.62 %, lessened hysteresis behavior and improved moisture stability is achieved. Our research emphasizes on the significance of the synergistic effect in additives for high-performance PSCs.

Yb3+‐Doped Phenylethylammonium Lead Bromide 2D Layered Hybrid Perovskite for Near‐Infrared Emission

AbstractTwo‐dimensional (2D) layered hybrid perovskites like phenylethylammonium lead bromide [(PEA)2PbBr4] show interesting optoelectronic properties and improved moisture stability owing to the repeating quantum‐well structure and hydrophobic organic cations, respectively. Doping metal ions in such perovskites leads to exciton‐dopant interactions, imparting new optical properties. Here we report synthesis and optical properties of Yb3+‐doped (PEA)2PbBr4. Crystals show plate‐like morphology with lateral size of few micrometers. Also, ∼3.5 nm thin nanoplatelets are obtained after sonicating the samples. The host absorbs light via excitonic (and band‐band) transition at 407 nm. A part of the generated excitons recombines by emitting light at 414 nm along with host‐related non‐radiative recombination. Another significant part of the excitons recombines by non‐radiatively transferring the energy to the f‐electrons of Yb3+ dopant ions. The Yb3+ ions then de‐excite via f‐f (2F5/2→2F7/2) transition emitting near‐infrared (NIR) radiation with a peak at 997 nm. Such NIR‐emitting semiconductors with improved performances are desired for NIR light‐emitting diode applications.

Spacer Organic Cation Engineering for Quasi‐2D Metal Halide Perovskites and the Optoelectronic Application

Recently, organic and inorganic halide perovskites are one of the most popular semiconductors owing to their enormous potential for optoelectronic application, such as photovoltaics (PV), light‐emitting diode (LED), photodetector, and so on. The photoelectric conversion efficiency of 3D organic–inorganic hybrid perovskite solar cells has increased rapidly; however, the commercialization of the related devices is largely hampered by the poor stability of perovskite materials under environmental stress. Compared to 3D halide perovskites, quasi‐2D (Q‐2D) perovskites have improved moisture stability and less tendency for ion migration, which offers a new approach to stabilize perovskite‐based optoelectronic devices. Furthermore, Q‐2D hybrid perovskites have diverse structures with different quantum confinement and dielectric confinement characteristics, which enables the fine‐tuning of their optoelectronic properties through structure engineering. Depending on the different structures of spacer organic cations, the Q‐2D perovskite structure mainly includes Ruddlesden−Popper (RP) phase structure, Dion−Jacobson (DJ) phase structure, and alternating cation in the interlayer space (ACI) phase structure. In this review, the state‐of‐the‐art in Q‐2D perovskites is discussed based on their structural engineering, and an overview of PV and LEDs applications is provided. Finally, a brief outlook with respect to the development of Q‐2D perovskite materials, as well as advanced device, is provided.

Electronic transport, ionic activation energy and trapping phenomena in a polymer-hybrid halide perovskite composite

The exploitation of methylammonium lead iodide perovskite-polymer composites is a promising strategy for the preparation of photoactive thin layers for solar cells. The preparation of these composites is a simple fabrication method with improved moisture stability when compared to that of pristine perovskite films. To deepen the understanding of the charge transport properties of these films, we investigated charge carrier mobility, traps, and ion migration. For this purpose, we applied a combinatory measurement approach that proves how such composites can still retain an ambipolar charge transport nature and the same mobility values of the related perovskite. Furthermore, thermally stimulated current measurements revealed that the polymer influenced the creation of additional defects during film formation without affecting charge mobility. Finally, impedance spectroscopy measurements suggested the addition of starch may hinder ion migration, which would require larger activation energies to move ions in composite films. These results pave the way for new strategies of polymer-assisted perovskite film development.

Thiamine additive engineering enables improved film formation towards high efficiency and moisture stability in perovskite solar cells

Perovskite solar cells (PSCs) attract widespread research interest due to their exceptional properties. However, the instability of the perovskite layer, especially the moisture instability, and existing defects seriously restrict the performance and limit the development of PSCs towards commercialization. Herein, we fabricate moisture-stable and efficient PSCs by incorporating a thiamine (THM) additive into a lead iodide (PbI2) precursor using a two-step spin-coating method. This strategy enables a better interaction between the THM additive and PbI2. Then, a higher energy barrier is produced when the material reacts with A-site cations to form perovskite crystals, resulting in larger grains and better-quality perovskite films. Through optimization of the concentration of the THM additive, the optimal perovskite achieves improved moisture stability and decreased trap states; thus, the corresponding unencapsulated devices achieve a remarkable power conversion efficiency (PCE) of 21.40% and maintain >92% of their initial PCE after 180 h in ambient air (∼50% humidity). The excellent performance is mainly attributed to the fact that THM promotes crystal growth and passivates defects in perovskite films.

Improved moisture stability of graphene transistors by controlling water molecule adsorption

Although atomically thin two-dimensional graphene is of interest for next-generation electronic device applications owing to its outstanding properties, a crucial issue concerning the stable operation of graphene-based devices under ambient conditions still remains for industrial applications. Because the electrical performance of graphene-based devices is largely affected by polar atmospheric species such as water molecules (H2O), it is important to eliminate this detrimental effect. In the present study, we report a facile method to enhance the moisture stability of graphene field-effect transistors (FETs) by modulating the surface energy of substrates. We found that this simple method enables us not only to retain the way to secure field-effect mobility, but also to improve the stability of graphene FETs. The device on the surface-modulated substrates showed excellent moisture stability, even under harsh humid environments. We expect that the proposed method will be widely useful for the improvement of ambient stability in various 2D material-based electronics.

The effects of pyridine molecules structure on the defects passivation of perovskite solar cells

Pyridine molecules have been widely used to improve the performances of perovskite solar cells (PSCs). However, the effects of pyridine molecular structure, especially the functional group, on the defects passivation of perovskite solar cell have a lack of investigation. In this work, we introduced three pyridine molecules as additives into perovskite layer, including pyridine (PY), 4-methyl-pyridine (MP) and 4-tertbutyl pyridine (TBP), to investigate the influences of the molecular structure on the surface-defect passivation and long-term stability of perovskite solar cells. In fact, the pyridine molecules play two roles in the perovskite films. On the one hand, due to the different molecular structure, these pyridine molecules present differences in electron-pair-donor abilities (TBP > MP > PY), and then affect the interaction of pyridine molecule with Pb2+ in perovskite. Importantly, with the increase of interaction between different functional groups and Pb2+, the defect passivation effect was enhanced. What’s more, the crystal quality and light harvesting ability of the corresponding perovskite layer are improved by large crystal size and slow growth process. Consequently, PSCs with TBP, MP and PY respectively obtained a power conversion efficiency of 17.03%, 15.49% and 14.34%, which are higher than that of without additive (13.34%). On the other hand, owing to the hydrophobicity of groups, the pyridine molecules can enhance the moisture stability of devices. Significantly, the device based on the TBP-modified perovskite film exhibited improved moisture stability among the four type devices, owing to the best characteristic of the tertiary-butyl group with hydrophobicity in TBP.