Simultaneous Defect Passivation and Electric Level Regulation with Rubidium Fluoride for High-Efficiency CsPbI2Br Perovskite Solar Cells.

Due to the good balance of efficiency and stability, CsPbI2Br perovskite solar cells (PSCs) recently have attracted widespread attention. However, the improvement in photovoltaic performance for CsPbI2Br PSCs was mainly limited by massive defects and unmatched energy levels. Surface modification is the most convenient and effective strategy to decrease defect densities of perovskite films. Herein, we deposited rubidium fluoride (RbF) onto the surface of CsPbI2Br perovskite films by spin-coating. The numerous defects could be significantly passivated by RbF, resulting in suppressed nonradiative recombination. Furthermore, the CsPbI2Br perovskite film after RbF treatment exhibits a deeper Fermi level, and an additional built-in electric field forms to promote charge transport. Consequently, the champion device achieves a high efficiency of 10.82% with an improved VOC of 1.14 V, and it also exhibits excellent stability after long-term storage. This work offers a simple and effective approach to enhance the photovoltaic performance and stability of PSCs for broader applications in the future.

Novel Strategy for High Efficient and Stable Perovskite Solar Cells through Atomic Layer Deposition.

The perovskite material has demonstrated conceivable potential as an absorbing material of solar cells. Although the power conversion efficiency of the device based on perovskite has rapidly come to 26%, there are still many factors that affect the further improvement of the photoelectric conversion efficiency. Interface defects are the dominating concern that influence carrier transportation and stability. Here, we report a novel strategy where B2O3 is deposited on the fresh perovskite film by atomic layer deposition technology. The organic atmosphere during atomic layer deposition can effectively regulate the crystallization kinetics of perovskites and promote crystal growth. The B2O3 adsorbed on the perovskite light-absorption layer can effectively reduce the electropositive defects on the surface of the perovskite, such as uncoordinated Pb2+ and I vacancies due to the electron-donating properties of the side O atoms in B2O3. Consequently, the power conversion efficiency of the perovskite solar cell after B2O3 treatment increases to 21.78% from 18.89%. Simultaneously, B2O3 can improve the stability of devices.

Giant tunnel resistance effect in (SrTiO3)2/(BaTiO3)4/(CaTiO3)2 asymmetric superlattice with enhanced polarization.

In this work, we report the effectively enhanced tunneling electroresistance effect in Au/(SrTiO3)2/(BaTiO3)4/(CaTiO3)2/Nb:SrTiO3 superlattice ferroelectric tunnel junction (FTJ). The stable polarization switching and enhanced ferroelectricity were achieved in the nanoscale thickness high-quality epitaxial superlattice. A high ON/OFF current ratio of more than 105 was obtained at room temperature, which is an order of magnitude larger than the BaTiO3 FTJ with the same structure. Nonvolatile resistance switching controlled by nonvolatile polarization switching was observed in the superlattice FTJ. Driven by increased polarization and intrinsic asymmetric ferroelectricity, a highly asymmetric depolarization field is generated compared with the Au/BaTiO3/Nb:SrTiO3 FTJ, resulting in an enhanced tunneling electroresistance effect. These results provide a potential way to construct FTJ memory devices by constructing asymmetric three-component ferroelectric superlattices.

W-doped VO2 for high-performance aqueous Zn-ion batteries.

Aqueous Zn-ion batteries (AZIBs) have become one of the most promising energy storage devices due to their high safety and low cost. However, the development of stable cathodes with fast kinetics and high energy density is the key to achieving large-scale application of AZIBs. In this work, W-doped VO2 (W-VO2) is developed by a one-step hydrothermal method. Benefiting from the pre-insertion of W6+ and the introduction of the W-O bond, accomplishing an expanded lattice spacing and a stable structure, both improved kinetics and long cycle life are achieved. The W-VO2 delivers a specific capacity of 340.2 mA h g-1 at 0.2 A g-1, an excellent high-rate capability with a discharge capacity of 186.9 mA h g-1 at 10 A g-1, and long-term cycling stability with a capacity retention of 76.5% after 2000 cycles. The electrochemical performance of the W-VO2 has been greatly improved, compared with the pure VO2. The W doping strategy proposed here also presents an encouraging pathway for developing other high-energy and stable cathodes.

A ternary oxygen-vacancy abundant ZnMn2O4/MnCO3/nitrogen-doped reduced graphene oxide hybrid towards superior-performance lithium storage.

Transition metal oxides (TMOs) and metal carbonates exhibit high specific capacity, abundant reserves on Earth, and environmental friendliness as anode materials for lithium-ion batteries (LIBs). However, their poor electrical conductivity and serious volume expansion lead to rapid capacity decay. Herein, a stable and highly conductive composite of an oxygen-vacancy abundant nitrogen-doped reduced graphene oxide (NG) encapsulated ZnMn2O4/MnCO3 (ZnMn2O4/MnCO3/NG) hybrid is successfully fabricated, which can provide more spaces for rapid ion diffusion and corroborate fast electron transport. The ZnMn2O4/MnCO3/NG hybrid exhibits an incredible reversible capacity (916 mA h g-1 at 0.1 A g-1), preeminent cycling stability (800 mA h g-1 at 1 A g-1 after 300 cycles) and outstanding rate capability (459 mA h g-1 at 2 A g-1). The excellent lithium storage performance of ZnMn2O4/MnCO3/NG is attributed to the synergistic effect between ZnMn2O4 and MnCO3, the addition of nitrogen and oxygen defects, and the stable structures of NG, which relieve the volume expansion of the electrode material, improve the electronic conductivity and enhance structural stability and surface capacitive response. This work provides a new idea for constructing oxygen-vacancy abundant NG encapsulated bimetal oxides for energy storage of LIBs.

Enhanced photoluminescence of double perovskite Cs2SnI6 nanocrystals via Na+ doping.

Double perovskites without lead element have attracted great attention in recent years. Further increasing the photoluminescence quantum yield of lead-free double perovskites is necessary for their potential applications. In this work, Na+ doped Cs2SnI6 nanocrystals were synthesized by hot injection method. It was displayed that all the NCs have uniform hexagonal shape with good crystallization. Energy dispersing spectroscopy and X-ray photoelectron spectroscopy proves the Na+ ions were doped in the lattice of perovskite structure. The photoluminescence intensity of doped NCs is increased by 2.7-fold than that of pure NCs. A maximum photoluminescence quantum yield of 72% is obtained. The luminous mechanism was investigated by femtosecond transient absorption spectrum and a self-trap emission was proved by the observation of ground state bleaching and photo-induced absorption signals.

Asymmetric liquid crystalline dibenzo[a,h]anthracenes for organic semiconductors with high mobility and thermal stability.

A series of asymmetric organic semiconductors based on N-shaped dibenzo[a,h]anthracene (DBA), Ph-DBA-Cn (n = 8, 10, 12), were developed. All Ph-DBA-Cn compounds had good chemical stability and smectic LC qualities, and thermally stable crystal phase can be maintained under 190 °C due to the suppressed molecular motions by the bent DBA core. High-quality crystalline films can be fabricated using a blade-coating technique. It was revealed that the average mobility of all Ph-DBA-Cn organic thin-film transistors (OTFTs) was estimated to be over 2.8 cm2 V-1 s-1, and a Ph-DBA-C8 device in particular afforded exceptional mobility of up to 11.8 cm2 V-1 s-1. The highly-ordered and uniaxially-oriented crystalline films composed of bilayer units were revealed to be responsible for their excellent electrical device performances. Furthermore, all Ph-DBA-Cn OTFTs can retain operational characteristics up to 160 °C over 1 cm2 V-1 s-1. These findings will be crucial for the development of high-mobility and thermally durable OSCs for practical electronics.

Near Zero-Threshold Voltage P-N Junction Diodes Based on Super-Semiconducting Nanostructured Ag/Al Arrays.

Semiconductor devices are currently one of the most common energy consumption devices. Significantly reducing the energy consumption of semiconductor devices with advanced energy-efficient technologies is highly desirable. The discovery of super-semiconductors (SSCs) based on metallic bi-layer shell arrays provides an opportunity to realize ultra-low-power consumption semiconductor devices. As an example, the achievement of near zero-threshold voltage in p-n junction diodes based on super-semiconducting nanostructured Ag/Al arrays is reported, realizing ultra-low-power p-n junction diodes: ≈3 W per trillion diodes with a working voltage of 1 V or 30 mW per trillion diodes with an operating voltage of 0.1 V. In addition, the p-n junction diodes exhibit a high breakdown field of ≈1.1 × 106  V cm-1 , similar to that of SiC and GaN, due to a robust built-in field driven by infrared light photons. The SSC p-n diodes with near zero-threshold voltage and high breakdown field allow access to ultra-low-power semiconducting transistors, integrated circuits, chips, etc.

Alkalis-doping of mixed tin-lead perovskites for efficient near-infrared light-emitting diodes.

Substitution of lead (Pb) with tin (Sn) is a very important way to reduce the bandgap of metal halide perovskite for applications in solar cells, and near infrared (NIR) light-emitting diodes (LEDs), etc. However, mixed Pb/Sn perovskite becomes very disordered with high trap density when the Sn molar ratio is less than 20%. This limits the applications of mixed Pb/Sn perovskites in optoelectronic devices such as wavelength tunable NIR perovskite LEDs (PeLEDs). In this work, we demonstrate that alkali cations doping can release the microstrain and passivate the traps in mixed Pb/Sn perovskites with Sn molar ratios of less than 20%, leading to higher carrier lifetime and photoluminescence quantum yield (PLQY). The external quantum efficiency (EQE) of Sn0.2Pb0.8-based NIR PeLEDs is dramatically enhanced from 0.1% to a record value of 9.6% (emission wavelength: 868 nm). This work provides a way of making high quality mixed Pb/Sn optoelectronic devices with small Sn molar ratios.

NiFe-LDH/MXene nano-array hybrid architecture for exceptional capacitive lithium storage.

Layered double hydroxides (LDHs) have great advantages in the domain of energy storage because of their exchangeable anions and large specific surface area. Nevertheless, the shortcomings of their poor electrical conductivity, easy stacking of nanosheets, and large volume variation in the cycling processes lead to unsatisfactory cycling stability and rate performance, which severely limits their further application. Therefore, we generated homogeneous nanoarrays of NiFe-LDH on the surface of Ti3C2Tx-MXene by a refluxing process. The resulting NiFe-LDH/MXene-500 hybrid material was applied as an anode of a lithium-ion battery (LIB) and exhibited a discharge capacity of 894.8 mA h g-1 at 200 mA g-1 (over 300 cycles) and could maintain a reversible capacity of 547.1 mA h g-1 even at 1 A g-1. With the addition of MXene, the volume increases of the NiFe-LDH/MXene hybrid materials were also significantly alleviated. The thickness of the NiFe-LDH/MXene-500 electrode only increased by 31% after 50 cycles, which was far better than the prepared NiFe-LDH electrode. On the hand, the synergistic interaction of NiFe-LDH and MXene could stabilize the structure, reduce the activation barrier of ion/electron diffusion, and promote electron transfer in the electrode. MXene with high conductivity can be used as electrical and ionic conductance media to promote the transformation reaction of NiFe-LDH. According to the detailed kinetic analysis, the capacitance control behavior is the main electrochemical reaction of NiFe-LDH/MXene electrodes.

New Approach to Low-Power-Consumption, High-Performance Photodetectors Enabled by Nanowire Source-Gated Transistors.

Power consumption makes next-generation large-scale photodetection challenging. In this work, the source-gated transistor (SGT) is adopted first as a photodetector, demonstrating the expected low power consumption and high photodetection performance. The SGT is constructed by the functional sulfur-rich shelled GeS nanowire (NW) and low-function metal, displaying a low saturated voltage of 0.61 V ± 0.29 V and an extremely low power consumption of 7.06 pW. When the as-constructed NW SGT is used as a photodetector, the maximum value of the power consumption is as low as 11.96 nW, which is far below that of the reported phototransistors working in the saturated region. Furthermore, benefiting from the adopted SGT device, the photodetector shows a high photovoltage of 6.6 × 10-1 V, a responsivity of 7.86 × 1012 V W-1, and a detectivity of 5.87 × 1013 Jones. Obviously, the low power consumption and excellent responsivity and detectivity enabled by NW SGT promise a new approach to next-generation, high-performance photodetection technology.

X-ray-Triggered CO Release Based on GdW10/MnBr(CO)5 Nanomicelles for Synergistic Radiotherapy and Gas Therapy.

Carbon monoxide (CO) therapy has become a hot topic in the field of gas therapy because of its application prospect in the treatment of various diseases. Due to the high affinity for human hemoglobin, the main challenge of CO-loaded nanomedicine is the lack of selectivity and toxicity in the delivery process. Although many commercial CO-releasing molecules (CORMs) have been widely developed because of their ability to deliver CO, CORMs still have some disadvantages, including difficult on-demand controlled CO release, poor solubility, and potential toxicity, which are limiting their further application. Herein, an X-ray-triggered CO-releasing nanomicelle system (GW/MnCO@PLGA) based on GdW10 nanoparticles (NPs) (GW) and MnBr(CO)5 (MnCO) encapsulating in the poly(lactic-co-glycolic acid) (PLGA) polymer was constructed for synergistic CO radiotherapy (RT). The production of strongly oxidative superoxide anion (O2-•) active species can lead to cell apoptosis under the X-ray sensitization of GW. Moreover, strongly oxidative O2-• radicals further oxidize and compete with the Mn center, resulting in the on-demand release of CO. The radio/gas therapy synergy to enhance the efficient tumor inhibition of the nanomicelles was investigated in vivo and in vitro. Therefore, the establishment of an X-ray-triggered controlled CO release system has great application potential for further synergistic RT CO therapy in deep tumor sites.

Encapsulated ruthenium nanoparticles activated few-layer carbon frameworks as high robust oxygen evolution electrocatalysts in acidic media.

Noble metals have been extensively employed as high active catalysts for oxygen evolution reaction (OER), are usually subjected to serious surface transformation and poor structural stability, especially in acid media, which need imperatively remedied. Herein, the interfacial engineering of Ru via few-layer carbon (Ru@FLC) was carried out, in which FLC can significantly suppress the corrosion of Ru in acid media, ensuring the efficient interfacial charge transport between Ru and FLC. As a result, a low overpotentials@10 mA cm-2 of 258 mV and small Tafel slopes of 53.1 mV dec-1 for oxygen evolution OER were achieved in acid media. DFT calculations disclose that outer FLC could induce charge redistribution and effectively optimize intermediates free energy adsorption, resulting in greatly reduce the energy barrier for OER. Our work may offer a new avenue to produce progressive OER electrocatalysts for energy-related applications in acid solution.

A magnet-renewable electroanalysis strategy for hydrogen sulfide in aquaculture freshwater using magnetic silver metal-organic frameworks.

A magnet-renewable electroanalytical strategy has been initially developed for monitoring hydrogen sulfide (H2S) in aquaculture freshwater systems using magnetic Fe3O4-loaded silver metal-organic framework (Fe3O4@Ag-MOF). The magnetic composites were synthesized by a hydrothermal route and further attached onto the magnetic electrodes. It was discovered that the Fe3O4@Ag-MOF-based electrochemical sensors could exhibit the extremely sharp and steady signals of solid-state Ag/AgCl electrochemistry at a lower potential. Furthermore, the highly specific and irreversible S-Cl replacement reactions could occur in the presence of H2S, so as to induce the conversion of AgCl into non-electroactive Ag2S with the rational decline of Ag/AgCl signals. Importantly, the Fe3O4@Ag-MOF-modified electrodes could be renewed simply by the removal of the magnet after each of the detection cycles for the next immobilization of Fe3O4@Ag-MOF probes. The developed electroanalytical method could facilitate the detection of H2S in the linear range from 4.0 to 1400 nM, with a limit of detection down to 2.0 nM. Besides, it was employed to detect H2S in aquaculture freshwater samples of fish, crab, and shrimp, showing the satisfactory results.

Modifying Jahn-Teller distortion by epitaxial stress in LaMnO3films for tunning electron localization.

The effect of epitaxial stress on Jahn-Teller (JT) distortion in epitaxial LaMnO3(LMO) films has been investigated. Both2θ-ωscans and reciprocal space maps (RSMs) indicate that LMO samples are subjected to compressive stress. Obvious Laue oscillations can be detected in2θ-ωscans, indicating the high quality of samples. RSMs of symmetry peak (001) and asymmetry peak (-103) imply different epitaxial stress for LMO films deposited on different substrates. Raman spectra measurements reveal that the degree of JT distortion can be well tuned via the epitaxial stress which may further influence on the electron localization in the films. This study might benefit to understanding the correlation between crystalline structure and electrical transport properties of LMO films and related LMO-based superlattices.

Enhanced photoluminescence of CsPbBr3-xIx nanocrystals via plasmonic Au nanoarrays.

Large scale ordered Au nanoarrays are fabricated by nanosphere lithography technique. The photoluminescence improvement of CsPbBr3-xIx nanocrystals by more than three times is realized in the CsPbBr3-xIx nanocrystal/Au nanoarray/Si structure. Time-resolved photoluminescence decay curves indicate that the lifetime is decreased by introducing the Au nanoarrays, which results in a increasing radiation recombination rate. The reflection spectra with two major valleys (the dip in the curve) located at ∼325 nm and 545 nm of Au nanoarray/Si structure, which illustrates two plasmonic resonance absorption peaks of the Au nanoarrays. The enhancement of photoluminescence is ascribed to a well match between the excitation/emission of CsPbBr3-xIx nanocrystals and localized surface plasmon/gap plasmon resonance absorption of the ordered Au nanoarrays, as also revealed from the finite-difference time-domain simulation analysis. Our work offers an effective strategy to improve the fluorescence of perovskite nanocrystals and provide the potential for further applications.

Enhanced upconversion red light emission of TiO2:Yb,Er thin film via Mn doping.

TiO2:Yb,Er films with different concentrations of Mn2+ are grown on SiO2 glass substrates by pulsed laser deposition. It is found that the introduction of Mn2+ enhanced the intensity of upconversion emission. In particular, TiO2:Yb,Er thin film with 5% Mn2+ ions exhibits the brightest upconversion emission. The upconversion red emission intensity is increased by 2.5-fold than that of a TiO2:Yb,Er thin film without Mn2+ ions, which is ascribed to the multi-photon absorption and efficient exchange-energy transfer process between Er3+ and Mn2+. The high transmittance and good conductivity of the films made them possible to act as electron transport layer in solar cells.

Enhancing the bulk photovoltaic effect by tuning domain walls in epitaxial BiFeO3films.

In this letter, the role of domain wall (DW) on bulk photovoltaic effect (BPV) effect in BiFeO3(BFO) films was studied by x-ray reciprocal space mapping and conductive atomic force microscope. It was found that the domain structure and DW can be tuned by controlling the epitaxial orientation of BFO film. Remarkably, under 1 sun AM 1.5 G illumination, the 109° DW enhances the transport of photogenerated carriers and simultaneously improves the conductivity and power conversion efficiency (PCE). The short-circuit current density and PCE can reach 171.15µA cm-2and 0.1127%, respectively. Therefore, our study reveals the correlation between the DW and the BPV effect in BFO film and provides a new pathway to improve the PCE of BFO-based photovoltaic device.

A highly selective and recyclable sensor for the electroanalysis of phosphothioate pesticides using silver-doped ZnO nanorods arrays.

Silver-doped ZnO nanorods (Ag/ZnO) arrays have in-situ grown onto indium tin oxide (ITO) via the one-pot hydrothermal route towards a highly selective and recyclable electroanalysis of phosphothioate pesticides (PTs) with phoxim (Phox) as a model. It was discovered that the Ag/ZnO arrays-modified electrode could obtain a steady and sharp electrochemical output of solid-state Ag/AgCl at a low potential (i.e., 0.12 V). More importantly, the achieved Ag/AgCl signals could decrease selectively induced by sulfide (S)-containing Phox by the specific Cl-S displacement reaction, which would trigger AgCl into non-electroactive Ag-Phox complex. The Ag/ZnO arrays-modified sensors present a linear range from 0.050 to 700.0 µM for the detection of Phox, with a limit of detection down to 0.010 µM. The practical applicability of the developed electroanalysis strategy was successfully employed to detect Phox in the tap water and cabbage samples. Moreover, the photocatalytic performances of the Ag/ZnO arrays were subsequently verified for the degradation of Phox, displaying the higher photocatalytic efficiency than pure ZnO nanorods. Besides, the as-developed sensor can allow for the recyclable detection of Phox by the Ag/ZnO-photocatalyzed removal of Phox after each of the detection cycles. Therefore, the sensors platform based on Ag/ZnO arrays can be expected to have potential for the electrochemical monitoring and photocatalytic degradation of toxic pesticides in the food and environmental fields.

Postpassivation of Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3 Perovskite Films with Tris(pentafluorophenyl)borane.

Passivating defects to suppress recombination is a valid tactic to improve the performance of third-generation perovskite-based solar cells. Pb0 is the primary defect in Pb-based perovskites. Here, tris(pentafluorophenyl)borane is inserted between the perovskite and spiro-OMeTAD layer in SnO2-based planar perovskite solar cells. The incorporation of tris(pentafluorophenyl)borane can effectively passivate Pb0 defects, decreasing recombination at the surface of the perovskite film. Additionally, the modification with tris(pentafluorophenyl)borane decreases the grain boundaries quantity in the perovskite film, enhancing the transportation capability of carriers. The resulting perovskite solar cell gets a high efficiency of 21.42%. While the reference device without tris(pentafluorophenyl)borane treatment acquires an efficiency of 19.07%. More importantly, the stability tests manifest that incorporating tris(pentafluorophenyl)borane in perovskite solar cells is conducive to the stability of the device.